After changing from incandecent lamps to LED's the existing flasher
did not work on the motercycle. Presumably the led's didn't draw
enough current to work.

I asked for help from this group and was one kindly given a schematic
to resolve the problem. I built it and sadly it did not work. I
believe the person who gave me the diagram had built it for himself so
I'm sure it works.

I'm not an electronic person per say. So what I'm hoping is that if I
provide the diagram with the various voltages that I have tested for
found someone could help detect what is wrong. I have tried to go over
it over and over to make sure its right and isn't some silly mistake.
The one thing I had to "guess" on was the Mosfet. The OP didnt say
what Mosfet to use just gave some specs. I tried to buy it based on
that. Perhaps thats my problem?

Here is the my diagram.
Im testing it with a 12volt AC/DC 300ma adapter that seems to put out
15.11-12 volts. I'm using a testing light that lights up from
1-50volts. I have provided I hope all details. The numbers in ( )
brackets are the values I have found when testing with my volt meter.
--------------------------------------------------------

+o----------------------,
| + |
(15.12v) | |
.------------.-|<-.----o--------------o------------------. |
Lamp
| 1N4148 | | | .-.
| / - \ | | Mosfet | ( X )
| /------\ | | IRFZ34 | '-'
o | T R | | | 60v 30A | |
| |2n3906| o | 0.050 Ohm | |
|(14.6v) '------' | | | |
.-. | | | .-. | Front | |
| | 100k | | | | | 220k | .--o---. | |
| | E B C | | | | | | |
'-' '-' | | | | |
|(1.97v) | | '------' | |
o-----. o | | | | | |
| | TR 2N3906 | | | | | | |
| | | | | | | | |
| | | | G D S |
'--.
| | E | | |
|
| (Q1)>| (1.35v) | (Q2) |(15.12v) |16Vz
|
| |-----B--------o o---o |
1N4744|
| + /| | Mosfet | | |Zener
|
--- | C | VF5408 | D | |
|
--- |(1.97v) | ||-+ - /--/
|
10uf |(0v) | 10k (1.79v)| G||<- ^ ^
|
/16v | '----|___|-------|----o------||-+ | |(0v)
|
Elec | | | | | |
|
trol | | .-. o---o |
|
ytic | 3.4Vz | | |100k | S |
|
| 1N4728 /--/ | | | |
|
| Zener ^ '-' |(0v) | +
o
| |(0v)|(0v) | |
o----------------------o----o---------o------------------'
| - -
o------------------------o
(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)


------------------------------------------------------------
Here is the OP description of the circuit.
------------------------------------------------------------
The electronic turn signal flasher works over a load range of about 20
milliamps to 10+ amps (will flash a pair of standard auto headlamps)

Theory of Operation:

Initially, the turn signal is in an off state but provides voltage to
the signal flasher circuit in series with the lamp(s). The 10 uf
electrolytic capacitor begins to charge. When the capacitor voltage
exceeds the base voltage by six tenths of a volt Q1 starts conducting
and puts the capacitor voltage on the gate of the N channel power
MOSFET Q2, turning on the mosfet. The initial conduction of the mosfet
causes the base voltage on Q1 to drop, which, in turn, causes Q1 to
conduct harder and drive the mosfet harder . This action keeps the
mosfet from spending time in its linear region, turning it on hard,
minimizing power dissipation in the mosfet.

The capacitor discharges through the 100 K resistor. When the voltage
on the gate of the mosfet falls below its conduction threshold, its
"on" resistance begins to rise. This causes the voltage on the emitter
of Q1 to rise, and since the base of Q1 has dropped it tends to turn
off quickly, allowing Q2 to turn off more etc., until the circuit
switches back to its initial state turning the series connected turn
signal lamp off.

I don't know the part number of the mosfet but the specifications are:
Voltage source to drain 60, Resistance in the "on" state is .04 ohms,
maximum current 30 amps, TO220 package. No heatsink is required with
up to about 15 amps or more. The entire circuit was mounted on 1" X 1"
piece of perf board. All resistors 1/4 watt. I put the circuit in a
small empty dental floss container and filled it with epoxy, running
the wires out to a pair of 1/4" male "quick connects," that plug into
the turn signal flasher connector. The on time and off time can be
adjusted independently by changing the value of the 220K charging
resistor (off) or 100K discharge resistor (on), or changing the value
of the capacitor (both off and on).
---------------------------------------
Here is the original link to the discussion ....

http://groups.google.com/group/sci.elec ... e+flasher#


Regards

Steve

On Sun, 23 Dec 2007 05:26:33 -0800 (PST), steve
<stevesemple@lycos.com> wrote:

>After changing from incandecent lamps to LED's the existing flasher
>did not work on the motercycle. Presumably the led's didn't draw
>enough current to work.
>
>I asked for help from this group and was one kindly given a schematic
>to resolve the problem. I built it and sadly it did not work. I
>believe the person who gave me the diagram had built it for himself so
>I'm sure it works.
>
>I'm not an electronic person per say. So what I'm hoping is that if I
>provide the diagram with the various voltages that I have tested for
>found someone could help detect what is wrong. I have tried to go over
>it over and over to make sure its right and isn't some silly mistake.
>The one thing I had to "guess" on was the Mosfet. The OP didnt say
>what Mosfet to use just gave some specs. I tried to buy it based on
>that. Perhaps thats my problem?
>
>Here is the my diagram.
>Im testing it with a 12volt AC/DC 300ma adapter that seems to put out
>15.11-12 volts. I'm using a testing light that lights up from
>1-50volts. I have provided I hope all details. The numbers in ( )
>brackets are the values I have found when testing with my volt meter.
>--------------------------------------------------------
>
> +o----------------------,
> | + |
> (15.12v) | |
> .------------.-|<-.----o--------------o------------------. |
>Lamp
> | 1N4148 | | | .-.
> | / - \ | | Mosfet | ( X )
> | /------\ | | IRFZ34 | '-'
> o | T R | | | 60v 30A | |
> | |2n3906| o | 0.050 Ohm | |
> |(14.6v) '------' | | | |
> .-. | | | .-. | Front | |
> | | 100k | | | | | 220k | .--o---. | |
> | | E B C | | | | | | |
> '-' '-' | | | | |
> |(1.97v) | | '------' | |
> o-----. o | | | | | |
> | | TR 2N3906 | | | | | | |
> | | | | | | | | |
> | | | | G D S |
>'--.
> | | E | | |
>|
> | (Q1)>| (1.35v) | (Q2) |(15.12v) |16Vz
>|
> | |-----B--------o o---o |
>1N4744|
> | + /| | Mosfet | | |Zener
>|
> --- | C | VF5408 | D | |
>|
> --- |(1.97v) | ||-+ - /--/
>|
> 10uf |(0v) | 10k (1.79v)| G||<- ^ ^
>|
> /16v | '----|___|-------|----o------||-+ | |(0v)
>|
> Elec | | | | | |
>|
> trol | | .-. o---o |
>|
> ytic | 3.4Vz | | |100k | S |
>|
> | 1N4728 /--/ | | | |
>|
> | Zener ^ '-' |(0v) | +
>o
> | |(0v)|(0v) | |
> o----------------------o----o---------o------------------'
> | - -
> o------------------------o
>(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)
>
>
>------------------------------------------------------------
>Here is the OP description of the circuit.
>------------------------------------------------------------
>The electronic turn signal flasher works over a load range of about 20
>milliamps to 10+ amps (will flash a pair of standard auto headlamps)
>
>Theory of Operation:
>
>Initially, the turn signal is in an off state but provides voltage to
>the signal flasher circuit in series with the lamp(s). The 10 uf
>electrolytic capacitor begins to charge. When the capacitor voltage
>exceeds the base voltage by six tenths of a volt Q1 starts conducting
>and puts the capacitor voltage on the gate of the N channel power
>MOSFET Q2, turning on the mosfet. The initial conduction of the mosfet
>causes the base voltage on Q1 to drop, which, in turn, causes Q1 to
>conduct harder and drive the mosfet harder . This action keeps the
>mosfet from spending time in its linear region, turning it on hard,
>minimizing power dissipation in the mosfet.
>
>The capacitor discharges through the 100 K resistor. When the voltage
>on the gate of the mosfet falls below its conduction threshold, its
>"on" resistance begins to rise. This causes the voltage on the emitter
>of Q1 to rise, and since the base of Q1 has dropped it tends to turn
>off quickly, allowing Q2 to turn off more etc., until the circuit
>switches back to its initial state turning the series connected turn
>signal lamp off.
>
>I don't know the part number of the mosfet but the specifications are:
>Voltage source to drain 60, Resistance in the "on" state is .04 ohms,
>maximum current 30 amps, TO220 package. No heatsink is required with
>up to about 15 amps or more. The entire circuit was mounted on 1" X 1"
>piece of perf board. All resistors 1/4 watt. I put the circuit in a
>small empty dental floss container and filled it with epoxy, running
>the wires out to a pair of 1/4" male "quick connects," that plug into
>the turn signal flasher connector. The on time and off time can be
>adjusted independently by changing the value of the 220K charging
>resistor (off) or 100K discharge resistor (on), or changing the value
>of the capacitor (both off and on).
>---------------------------------------
>Here is the original link to the discussion ....
>
>http://groups.google.com/group/sci.electronics.basics/browse_frm/thread/4ecf37b3d76f74ba/83fb8a294a4deff6?lnk=gst&q=motorcycle+flasher#
>
>
>Regards
>
>Steve

Hi Steve

That's my schematic. There appears to be a problem in the area of the
PNP transistor. The base should be clamped to around 3 volts (while
the thing is in the off state - which is what you have stays off (?).

You show around 2 volts on the collector - that is not enough voltage
to turn on the mosfet - you want 4 or more volts there.

With it turned off (lamp in the off state), the voltage at the emitter
should rise to greater than 4 volts, the voltage at the base should be
clamped to around 3-4 volts - if you can remove the transistor - where
the emitter connects the voltage should be ~12+ volts, the base should
be 3-4 volts, and the collector (with no transistor in the circuit),
should be 0 V

I'd suspect a bad PNP transistor (or wrong transistor or connected
wrong). Or just a transistor with poor gain - the gain should be on
the order of 100-200 in that circuit.

Second suspect is the timing cap being leaky - in order to get 4 volts
out you have to have >4 at the emitter - and you don't. With the
transistor removed if you got 12+ Volts there after about a second for
the cap to charge - the cap is good.

The other thing that is likely cause, assuming the other things
checked out, is if the current to the gate of the mosfet is way too
high. That would pull down the other voltages.

A good mosfet has almost no gate current - the gate is an insulator -
that 100 K gate to ground is for the purpose of discharging the gate
capacitance. That has to be 100 K or so, you don't want a lower value
there, so check that. (band next to the gold or silver is yellow)

To check the mosfet - disconnect the gate (and you may want to
temporarily ground it so you don't destroy it with static) - with the
gate disconnected, the voltage at the collector of the PNP should rise
to >4 volts - if it does and does not when connected, the mosfet has
already encountered static.

If the voltage is <4 V at the collector of the PNP with the gate
disconnected (and the 100 K is indeed 100 K) the problem is before the
mosfet.

Once it is wired into the circuit - the mosfet gate is connected to
something and won't be sensitive to static electricity - but the bare
part can be easily destroyed. You can read about proper handling of
static sensitive parts - the object is to avoid a voltage differential
greater than ~50 volts on the gate and other terminals - easy to get
on a dry day, room with a carpet, or leakage in a soldering iron.

Good luck
Tell me what you find, or any questions on the troubleshooting I've
outlined.

I'll be out of town tomorrow but will check the group if my wife
doesn't have other plans.

bob
--

Hi bob.

Thanks for the advice. I actually built this shortly after you gave it
to me I think in sept. But it didnt work and I just didnt get around
to it again until now. I will try to check those things and get back.
Yes like you its a busy season, so no rush. Its waited since sept it
would be presumptuous to suddenly think its important.

Have a good season.

On Sun, 23 Dec 2007 09:54:28 -0800 (PST), steve
<stevesemple@lycos.com> wrote:

You too.

--

On Dec 23, 7:26 am, steve <stevesem...@lycos.com> wrote:
> After changing from incandecent lamps to LED's the existing flasher
> did not work on the motercycle. Presumably the led's didn't draw
> enough current to work.
>
> I asked for help from this group and was one kindly given a schematic
> to resolve the problem. I built it and sadly it did not work. I
> believe the person who gave me the diagram had built it for himself so
> I'm sure it works.
>
> I'm not an electronic person per say. So what I'm hoping is that if I
> provide the diagram with the various voltages that I have tested for
> found someone could help detect what is wrong. I have tried to go over
> it over and over to make sure its right and isn't some silly mistake.
> The one thing I had to "guess" on was the Mosfet. The OP didnt say
> what Mosfet to use just gave some specs. I tried to buy it based on
> that. Perhaps thats my problem?
>
> Here is the my diagram.
> Im testing it with a 12volt AC/DC 300ma adapter that seems to put out
> 15.11-12 volts. I'm using a testing light that lights up from
> 1-50volts. I have provided I hope all details. The numbers in ( )
> brackets are the values I have found when testing with my volt meter.
> --------------------------------------------------------
>
> +o----------------------,
> | + |
> (15.12v) | |
> .------------.-|<-.----o--------------o------------------. |
> Lamp
> | 1N4148 | | | .-.
> | / - \ | | Mosfet | ( X )
> | /------\ | | IRFZ34 | '-'
> o | T R | | | 60v 30A | |
> | |2n3906| o | 0.050 Ohm | |
> |(14.6v) '------' | | | |
> .-. | | | .-. | Front | |
> | | 100k | | | | | 220k | .--o---. | |
> | | E B C | | | | | | |
> '-' '-' | | | | |
> |(1.97v) | | '------' | |
> o-----. o | | | | | |
> | | TR 2N3906 | | | | | | |
> | | | | | | | | |
> | | | | G D S |
> '--.
> | | E | | |
> |
> | (Q1)>| (1.35v) | (Q2) |(15.12v) |16Vz
> |
> | |-----B--------o o---o |
> 1N4744|
> | + /| | Mosfet | | |Zener
> |
> --- | C | VF5408 | D | |
> |
> --- |(1.97v) | ||-+ - /--/
> |
> 10uf |(0v) | 10k (1.79v)| G||<- ^ ^
> |
> /16v | '----|___|-------|----o------||-+ | |(0v)
> |
> Elec | | | | | |
> |
> trol | | .-. o---o |
> |
> ytic | 3.4Vz | | |100k | S |
> |
> | 1N4728 /--/ | | | |
> |
> | Zener ^ '-' |(0v) | +
> o
> | |(0v)|(0v) | |
> o----------------------o----o---------o------------------'
> | - -
> o------------------------o
> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> ------------------------------------------------------------
> Here is the OP description of the circuit.
> ------------------------------------------------------------
> The electronic turn signal flasher works over a load range of about 20
> milliamps to 10+ amps (will flash a pair of standard auto headlamps)
>
> Theory of Operation:
>
> Initially, the turn signal is in an off state but provides voltage to
> the signal flasher circuit in series with the lamp(s). The 10 uf
> electrolytic capacitor begins to charge. When the capacitor voltage
> exceeds the base voltage by six tenths of a volt Q1 starts conducting
> and puts the capacitor voltage on the gate of the N channel power
> MOSFET Q2, turning on the mosfet. The initial conduction of the mosfet
> causes the base voltage on Q1 to drop, which, in turn, causes Q1 to
> conduct harder and drive the mosfet harder . This action keeps the
> mosfet from spending time in its linear region, turning it on hard,
> minimizing power dissipation in the mosfet.
>
> The capacitor discharges through the 100 K resistor. When the voltage
> on the gate of the mosfet falls below its conduction threshold, its
> "on" resistance begins to rise. This causes the voltage on the emitter
> of Q1 to rise, and since the base of Q1 has dropped it tends to turn
> off quickly, allowing Q2 to turn off more etc., until the circuit
> switches back to its initial state turning the series connected turn
> signal lamp off.
>
> I don't know the part number of the mosfet but the specifications are:
> Voltage source to drain 60, Resistance in the "on" state is .04 ohms,
> maximum current 30 amps, TO220 package. No heatsink is required with
> up to about 15 amps or more. The entire circuit was mounted on 1" X 1"
> piece of perf board. All resistors 1/4 watt. I put the circuit in a
> small empty dental floss container and filled it with epoxy, running
> the wires out to a pair of 1/4" male "quick connects," that plug into
> the turn signal flasher connector. The on time and off time can be
> adjusted independently by changing the value of the 220K charging
> resistor (off) or 100K discharge resistor (on), or changing the value
> of the capacitor (both off and on).
> ---------------------------------------
> Here is the original link to the discussion ....
>
> http://groups.google.com/group/sci.elec ... frm/thre...
>
> Regards
>
> Steve

Hey, Steve, I've done something similar on my 2004 Honda Sabre. I
wanted hazard flashers which the bike didn't come with. My solution
would very much work for your problem, I think.

There is a line that carries electricity from the battery through a
fuse and is controlled by the turn signal switch (of course). That
line probably feeds the flasher unit on your bike. Remove the flasher
unit and you now have a nice source of electricity to power your
alternate device (which I'll describe next) and run your lights.

I used the device I'll describe for powering both the left and right
signals (front and rear) for hazards but this will work for you, too.
I use a LM555 timer chip from National Semiconductor which you should
be able to get from most any electronics store (RS might have them,
they are very common) or try online (allelectronics.com,
alliedelectronics.com, if I remember the sites correctly). Check the
tech notes on National's site (http://www.national.com/mpf/LM/
LM555.html). Look at the technical documentation for the chip (when I
view the HTML version it's on Page 7 (marked on the page so it should
be the same no matter which version of the docs you look at) for
Astable Operation. Output is pin 3. One thing that I didn't realize
until I had used this chip for some time is that the output isn't just
HIGH it also goes LOW. Since the duty cycle can only be set to a
maximum of 50% on and 50% off (more or less) that means that the
output is HIGH for AT LEAST 50% of the time which I found to be too
fast for my flashers. But, since the output is LOW when it is not
HIGH (and not just simply disconnected as I assumed (foolishly) it
would be when I first started messing with these things, you can use
the output in it's LOW state to sink power from a solenoid in a relay
so that the LOW condition of the output is when the circuit lights
your lights instead of using the HIGH output as the drive for your
relay solenoid. Lemme finish the description of the circuit then I'll
come back to that.

Okay, once you have your 555 setup to run on/off/on/off... you need a
way to turn your lights on and off. The 555 cannot handle much
current through itself (something like 300mA, IIRC, check the docs to
be sure). I use a relay (I go to wrecking yards and pull fuses and
relays off the cars and trucks and the people usually don't charge me
as long as I'm getting something else that is more valuable that I pay
for (like a lamp assembly or whatever) so I have TONS of 12v relays I
got for free). The relay will draw probably 10-20mA when the solenoid
inside is energized (you can verify this with a mutimeter). Plenty
low for the 555 to handle by itself. If the auto relays draw too much
current (or if you're using a bunch of them) you could use a really
small relay just to switch the power to the larger relays.

Anyway, I run the positive from the switch to the base of the single-
pole, double-throw relay. (Most relays (automotive, anyway) seem to
be marked with each of their 5 legs as either 85, 86, 30, 87, and
87a, *OR* 1, 2, 3, 4, 5. 85/86 and 1/2 are for the solenoid, 30/3 is
the bottom of the Y for the switch, 87a/4 is the NORMALLY CLOSED (NC)
pin (when the solenoid is not energized 30/3 is connected to 87a/4)
and 87/5 is the NORMALLY OPEN (NO) pin (30/3 disconnects from 87a/4
and connects to 87/5 when the solenoid is energized). So, I tie the
+12v from the switch to 30/3. I tie the load I want to run (the
lights) to 87/5.

To put it all together: take the +12v from your turn signal switch and
tie it to a) the 555 timer circuit INPUT (+Vcc in the diagram in the
documents for the chip I mentioned) and b) to pin 30/3 on your
automotive relay. Tie the ground of the 555 timer marked as earth (3
horizontal lines at the bottom of the diagram connected to pin 1 of
the 555 and other parts of the circuit) to ground on the motorcycle.
Depending on whether you want the lights on longer or off longer you
will want to use the OUTPUT of the 555 when it is HIGH or LOW.
Personally, I liked the lights off longer so I used the output when it
was LOW. So, run the +12v from the turn signal switch to the solenoid
in the relay (pin 85/1) and run the other pin to the solenoid (86/2)
to the OUTPUT of the 555 timer (pin 3). Connect the pin from the
relay marked 87/5 to the lights you want to operate.

That's all for ONE side (left or right). You will need to build two
devices; one for the left and another for the right.

What happens: when you hit your turn signal switch +12v comes from the
battery through whatever circuitry (including that switch) to where
the original flasher was. You now use that power to power a 555 timer
chip (provides the on/off sequence or flashing), a relay that can
handle the current load of the lights, and the lights themselves.
When you turn the turn signal off the whole circuit loses power and
the lights quit flashing.

I hope I've laid that out clearly. It's really simple to me because
I've done it before but I may not describe it very well because I'm
intimate with the knowledge. The 555 timer chip is ridiculously
common so you can find a ton of information about it online. Do a
Google search for "555 timer chip" and you'll find a lot of sites
about it including sites that have duty cycle calculators that will
allow you to figure out what resistances to use in the circuit.

I hope that helps.

Merry Christmas.

--HC

HC

Thanks for your help.

I'm going to print off your suggestion and store it. I'm for the
moment sticking with Bob's schematic cause I'm anal and like to solve
things I start, however I may do yours next cause, I think like most
people on this group its not about the device as much the challenge,
growing experience and satisfaction of playing with electronics. Heck
if it was just about fixing the problem strickly I'm sure for 20
dollars I could buy a ready bought thing that would solve the problem.
I do have some 555's around so hopfully when I finish my current
project and then need help on yours, I will probably come and annoy
you all on it:)

Thank you very much.
Happy seasons.

steve wrote:
> HC
>
> Thanks for your help.
>
> I'm going to print off your suggestion and store it. I'm for the
> moment sticking with Bob's schematic cause I'm anal and like to solve
> things I start, however I may do yours next cause, I think like most
> people on this group its not about the device as much the challenge,
> growing experience and satisfaction of playing with electronics. Heck
> if it was just about fixing the problem strickly I'm sure for 20
> dollars I could buy a ready bought thing that would solve the problem.
> I do have some 555's around so hopfully when I finish my current
> project and then need help on yours, I will probably come and annoy
> you all on it:)
>
> Thank you very much.
> Happy seasons.

Steve,

If you decide to use HC's idea, you should add a transistor
between the output of the 555 and the relay. Some of those
automotive relays are rated at 88 ohms and can draw near
150 mA from the 555. The maximum current shown on the
datasheet graphs is 100 mA, so use of the transistor is
a good idea. Here's an example:

+12 ---------+---------+
|k |
[D1] [Relay1]
| |
+---------+
|
c/
555 Pin3 ---[240R]---| PN2222
e\
|
Gnd -------------------+

The diode (banded end connected to +) absorbs the inductive kick
when the relay shuts off. You can use an 1N4001 or any 1N400x.
The PN2222 transistor can handle up to 600 mA.

You can also use his idea with a single 555 circuit,
by adding diodes and a second relay:

+12-------0
|
left |> | <|right
| | D2
o o---->|---+--- to 555 pin 8
| |
+------+--->|---+
| |k D3
[Relay2] [D4]
| |
Gnd ---+------+

The above circuit will operate the 555 and Relay1 from the previous
diagram when the turn signal is in either the left or the right
position. It will operate relay2 only when the turn signal is in
the left position.

The output from the 555 relay (relay1) will be connected to the
operating contact of relay2. The normally closed contact of relay2
goes to the right lights; the normally open contact of relay2
goes to the left lights:

Contacts
Relay1
+12 ---o o-------o
| | |
|> | |> |<-. <=contacts relay 2
| |
| +--- to right lights
|
+--------- to left lights

Ed

On Dec 24, 8:18 am, steve <stevesem...@lycos.com> wrote:
> HC
>
> Thanks for your help.
>
> I'm going to print off your suggestion and store it. I'm for the
> moment sticking with Bob's schematic cause I'm anal and like to solve
> things I start, however I may do yours next cause, I think like most
> people on this group its not about the device as much the challenge,
> growing experience and satisfaction of playing with electronics. Heck
> if it was just about fixing the problem strickly I'm sure for 20
> dollars I could buy a ready bought thing that would solve the problem.
> I do have some 555's around so hopfully when I finish my current
> project and then need help on yours, I will probably come and annoy
> you all on it:)
>
> Thank you very much.
> Happy seasons.

You're very welcome. As one person has followed up to say, some of
the relays may draw more amperage than the 555 can handle. In that
event use a smaller relay to switch the bigger relays as I mentioned
in my original response. Frying your 555 is easy to do (it is for me,
anyway, as I've ruined a few (I'm no electronics genius)).

Merry Christmas.

--HC

On Dec 24, 4:47 pm, ehsjr <eh...@bellatlantic.net> wrote:
> steve wrote:
> > HC
>
> > Thanks for your help.
>
> > I'm going to print off your suggestion and store it. I'm for the
> > moment sticking with Bob's schematic cause I'm anal and like to solve
> > things I start, however I may do yours next cause, I think like most
> > people on this group its not about the device as much the challenge,
> > growing experience and satisfaction of playing with electronics. Heck
> > if it was just about fixing the problem strickly I'm sure for 20
> > dollars I could buy a ready bought thing that would solve the problem.
> > I do have some 555's around so hopfully when I finish my current
> > project and then need help on yours, I will probably come and annoy
> > you all on it:)
>
> > Thank you very much.
> > Happy seasons.
>
> Steve,
>
> If you decide to use HC's idea, you should add a transistor
> between the output of the 555 and the relay. Some of those
> automotive relays are rated at 88 ohms and can draw near
> 150 mA from the 555. The maximum current shown on the
> datasheet graphs is 100 mA, so use of the transistor is
> a good idea. Here's an example:
>
> +12 ---------+---------+
> |k |
> [D1] [Relay1]
> | |
> +---------+
> |
> c/
> 555 Pin3 ---[240R]---| PN2222
> e\
> |
> Gnd -------------------+
>
> The diode (banded end connected to +) absorbs the inductive kick
> when the relay shuts off. You can use an 1N4001 or any 1N400x.
> The PN2222 transistor can handle up to 600 mA.
>
> You can also use his idea with a single 555 circuit,
> by adding diodes and a second relay:
>
> +12-------0
> |
> left |> | <|right
> | | D2
> o o---->|---+--- to 555 pin 8
> | |
> +------+--->|---+
> | |k D3
> [Relay2] [D4]
> | |
> Gnd ---+------+
>
> The above circuit will operate the 555 and Relay1 from the previous
> diagram when the turn signal is in either the left or the right
> position. It will operate relay2 only when the turn signal is in
> the left position.
>
> The output from the 555 relay (relay1) will be connected to the
> operating contact of relay2. The normally closed contact of relay2
> goes to the right lights; the normally open contact of relay2
> goes to the left lights:
>
> Contacts
> Relay1
> +12 ---o o-------o
> | | |
> |> | |> |<-. <=contacts relay 2
> | |
> | +--- to right lights
> |
> +--------- to left lights
>
> Ed

Clever. Nicely done. Wish I'd thought of that.

Merry Christmas.

--HC

On Mon, 24 Dec 2007 19:32:07 -0800 (PST), HC <hboothe@gte.net> wrote:

>On Dec 24, 8:18 am, steve <stevesem...@lycos.com> wrote:
>> HC
>>
>> Thanks for your help.
>>
>> I'm going to print off your suggestion and store it. I'm for the
>> moment sticking with Bob's schematic cause I'm anal and like to solve
>> things I start, however I may do yours next cause, I think like most
>> people on this group its not about the device as much the challenge,
>> growing experience and satisfaction of playing with electronics. Heck
>> if it was just about fixing the problem strickly I'm sure for 20
>> dollars I could buy a ready bought thing that would solve the problem.
>> I do have some 555's around so hopfully when I finish my current
>> project and then need help on yours, I will probably come and annoy
>> you all on it:)
>>
>> Thank you very much.
>> Happy seasons.
>
>You're very welcome. As one person has followed up to say, some of
>the relays may draw more amperage than the 555 can handle. In that
>event use a smaller relay to switch the bigger relays as I mentioned
>in my original response. Frying your 555 is easy to do (it is for me,
>anyway, as I've ruined a few (I'm no electronics genius)).
>
>Merry Christmas.
>
>--HC

I built three iterations of the flasher before settling on the mosfet
transistor. One was the 555. I wanted a two wire flasher since that's
what the bike had - the downside is that it takes a physically large
"hold up" capacitor to supply power to a relay while it is shorting
its own power supply, so a mosfet with or without the 555 is almost a
necessity.

I was able to find a 12V 600 ohm 8 amp relay but it wasn't from an
automobile. Relays in cars usually have lower resistance coils. Low
coil resistance means separate switching transistor, and larger
capacitor.

I tried an "Eccles-Jorden" (cross coupled flip flop) using two
transistors with the relay in one transistor's collector both it and
the 555 designs took a 1,000 - 2,000 uf cap to hold the voltage up
while the relay was shorting its own power source.

If one were designing a three wire flasher with ground and supply
available to the circuit all the time, a large cap is unnecessary.

Neat thing about mosfets is they tend to stay on with very little gate
drive current. With a load in the drain circuit and just touching the
gate to a positive voltage source - it turns on and stays on until the
charge bleeds off. In the case of a power mosfet, as much as several
seconds, so you have to provide a discharge path.
--

steve wrote:
> After changing from incandecent lamps to LED's the existing flasher
> did not work on the motercycle. Presumably the led's didn't draw
> enough current to work.
>

Why not use a simple 555 square wave oscillator and a single power
transistor to drive the flashers?

R

steve wrote:
> After changing from incandecent lamps to LED's the existing flasher
> did not work on the motercycle. Presumably the led's didn't draw
> enough current to work.
>
> I asked for help from this group and was one kindly given a schematic
> to resolve the problem. I built it and sadly it did not work. I
> believe the person who gave me the diagram had built it for himself so
> I'm sure it works.
>

Use this circuit with the lamps in place of MOT1.

http://www.uoguelph.ca/~antoon/circ/pwm555.html

Use P1 to adjust the on-off cycle.

R

On Wed, 26 Dec 2007 13:36:11 +1300, Roger Dewhurst
<dewhurst@wave.co.nz> wrote:

>steve wrote:
>> After changing from incandecent lamps to LED's the existing flasher
>> did not work on the motercycle. Presumably the led's didn't draw
>> enough current to work.
>>
>> I asked for help from this group and was one kindly given a schematic
>> to resolve the problem. I built it and sadly it did not work. I
>> believe the person who gave me the diagram had built it for himself so
>> I'm sure it works.
>>
>
>Use this circuit with the lamps in place of MOT1.
>
>http://www.uoguelph.ca/~antoon/circ/pwm555.html
>
>Use P1 to adjust the on-off cycle.
>
>R
It isn't a two wire flasher - a two wire flasher can be used in either
ground or hot lead and requires no separate (switched) connection to
12 volts.

The pot and cap would have to be larger to get the frequency down to
0.5 HZ, there's no need to vary the pulse width, so the pot and diodes
are not needed. Throw in a CMOS version of the 555, tweak the timing a
bit and that circuit could be adapted to work - by adding a small
diode to keep the cap charged so the 555 will continue working while
the mosfet is shorting its own power supply.

Piece of cake.
--

Well I'm back with some results Bob. There seems to have been a bit of
discussion in my absence. Unfortunetely I'm not Electronically
intellegent enought to add anything into any of the debate. However I
can tell you my results on the tests you suggested on your circuit.

I have put them in context of your text below. I have done 7 tests.
Please see them numbered.


> You show around 2 volts on the collector - that is not enough voltage
> to turn on the mosfet - you want 4 or more volts there.
>
> With it turned off (lamp in the off state), the voltage at the emitter
> should rise to greater than 4 volts, the voltage at the base should be
> clamped to around 3-4 volts - if you can remove the transistor - where
> the emitter connects the voltage should be ~12+ volts,

** 1. Connector 14.70volts (basically the AC adapter output) So this
seems to be OK.

>the base should be 3-4 volts,

** 2. Base 1.6 -- This is too low based on what you are saying.
However I tried two other transistors one the exact same and another
that has a little lower Hfe (because I had it on hand) and it really
didn't change.

>and the collector (with no transistor in the circuit), should be 0 V

** 3. Collector is 0.0
>
> I'd suspect a bad PNP transistor (or wrong transistor or connected
> wrong). =A0Or just a transistor with poor gain - the gain should be on
> the order of 100-200 in that circuit.

** 4. I tested the transistor using the little thing on my Volt meter
I get HFE 189

> Second suspect is the timing cap being leaky - in order to get 4 volts
> out you have to have >4 at the emitter - and you don't. =A0With the
> transistor removed if you got 12+ Volts there after about a second for
> the cap to charge - the cap is good.

** 5. I tried this, removed transistor and I get voltage of >14 volts.
I try to discharge the cap and then try it again and it seems to very
quickly go from low 0 to >14volts.
So that seems OK. I changed the cap just in case. Same result.

> The other thing that is likely cause, assuming the other things
> checked out, is if the current to the gate of the mosfet is way too
> high. =A0That would pull down the other voltages. =A0
>
> A good mosfet has almost no gate current - the gate is an insulator -
> that 100 K gate to ground is for the purpose of discharging the gate
> capacitance. =A0That has to be 100 K or so, you don't want a lower value
> there, so check that. =A0(band next to the gold or silver is yellow)

** 6. Tested all resistor they are all right.

> To check the mosfet - disconnect the gate (and you may want to
> temporarily =A0ground it so you don't destroy it with static) - with the
> gate disconnected, the voltage at the collector of the PNP should rise
> to >4 volts - if it does and does not when connected, the mosfet has
> already encountered static.

** 7. I get about 1.88volts. Interestingly the Light dimmly lights up
untill I put my probe on the gate. I also tried to test the mosfet
using the following ...

http://www.uoguelph.ca/~antoon/gadgets/mostest.htm
It seems to test ok.

Im sorry to be such a dolt on this. Its a simple circuit and yet there
is something Ive done that just isnt right. By the way on my original
schematic I put in the orientation of the transistor and Triac are
they right?
eg Transistor 2N3906 Holding legs from bottom legs pointing down,
looking at flat part of TR. with round part at the back EBC
Mosfet IRFZ34 Holding legs from bottom Looking at "front" of mosfet
Heatsink to top
GDS.
I have replaced the Mosfet and as I mentioned above exchanged the
transistor, tested all resistors to make sure they are the right R
value.
I even am using a different DC adapter. instead of 12v 300 mA Im now
using a 12v 800mA thinking maybe there just was not enough current. No
real change. I have hooked it up in the following way, Using two
diffierent lights. One is a test light that works up to 50v and the
other a 12volt car test light. Both work out of the circuit.

Negative ----- Circuit --- Lamp ---- Positive

>
> If the voltage is <4 =A0V at the collector of the PNP with the gate
> disconnected (and the 100 K is indeed 100 K) the problem is before the
> mosfet.
Im not sure what is considered before the mosfet.

Or do you think the mosfet specs I used are Ok. Im not sure where to
look next.
Again it is probably user error but I seem blind to what it is. Could
some of the resistors be lowered to increase power ??

Regards

On Fri, 28 Dec 2007 08:30:46 -0800 (PST), steve
<stevesemple@lycos.com> wrote:

>Well I'm back with some results Bob. There seems to have been a bit of
>discussion in my absence. Unfortunetely I'm not Electronically
>intellegent enought to add anything into any of the debate. However I
>can tell you my results on the tests you suggested on your circuit.
>
>I have put them in context of your text below. I have done 7 tests.
>Please see them numbered.
>
>
Go right to the bottom of the my post - that should get you up and
running right away

>> You show around 2 volts on the collector - that is not enough voltage
>> to turn on the mosfet - you want 4 or more volts there.
>>
>> With it turned off (lamp in the off state), the voltage at the emitter
>> should rise to greater than 4 volts, the voltage at the base should be
>> clamped to around 3-4 volts - if you can remove the transistor - where
>> the emitter connects the voltage should be ~12+ volts,
>
>** 1. Connector 14.70volts (basically the AC adapter output) So this
>seems to be OK.
>
>>the base should be 3-4 volts,
>
>** 2. Base 1.6 -- This is too low based on what you are saying.
>However I tried two other transistors one the exact same and another
>that has a little lower Hfe (because I had it on hand) and it really
>didn't change.
The base should only be 3-4 volts with the transistor out of the
circuit - otherwise it will vary.

That reading (if indeed with the transistor out) is wrong. So that's
where I'd look first (I'm assuming the cap charged to ~ 14 volts in
the previous test). That part of the circuit (sans transistor) is
nothing more than a resistor feeding a zener and establishing a
voltage reference. Only two parts - not much to go wrong. A resistor
that is too high or zener that is leaky or wrong value will establish
a wrong voltage there.

There are two other ways to establish a voltage there other than a
zener if you don't have the right one or spare

1. Use a simple voltage divider instead (the 220K will be changed for
a 4.7 K and zener will be replaced with a 1.5 K) circuit operation is
virtually the same with some degradation in flashing rate tracking the
power supply voltage (rev the motor flashes faster) With a 14V
supply that should be a little over 3 volts with no transistor in the
circuit.

2. A string of 6 series connected forward biased silicon diodes to
replace the single zener diode (arrows or body bands pointing to
ground - backwards from the single zener) - each diode gives a drop of
..6 volts and six should be 3.6 volts (again, sans transistor).

These are ways to substitute the zener and establish the 3-4 volts the
base connection requires - and the circuit should work that way when
the transistor is replaced (but check to see that there is 3-4 volts
there first to save time and effort)

>
>>and the collector (with no transistor in the circuit), should be 0 V
>
>** 3. Collector is 0.0
>>
>> I'd suspect a bad PNP transistor (or wrong transistor or connected
>> wrong). Or just a transistor with poor gain - the gain should be on
>> the order of 100-200 in that circuit.
>
>** 4. I tested the transistor using the little thing on my Volt meter
>I get HFE 189

That's good
>
>> Second suspect is the timing cap being leaky - in order to get 4 volts
>> out you have to have >4 at the emitter - and you don't. With the
>> transistor removed if you got 12+ Volts there after about a second for
>> the cap to charge - the cap is good.
>
>** 5. I tried this, removed transistor and I get voltage of >14 volts.

OK that clears up my other concern - you DO have ~14 volts at the +
terminal of the cap.
>I try to discharge the cap and then try it again and it seems to very
>quickly go from low 0 to >14volts.
>So that seems OK. I changed the cap just in case. Same result.
>
Yes that's what it should be doing
>> The other thing that is likely cause, assuming the other things
>> checked out, is if the current to the gate of the mosfet is way too
>> high. That would pull down the other voltages.
>>

>> A good mosfet has almost no gate current - the gate is an insulator -
>> that 100 K gate to ground is for the purpose of discharging the gate
>> capacitance. That has to be 100 K or so, you don't want a lower value
>> there, so check that. (band next to the gold or silver is yellow)
>
>** 6. Tested all resistor they are all right.
>
>> To check the mosfet - disconnect the gate (and you may want to
>> temporarily ground it so you don't destroy it with static) - with the
>> gate disconnected, the voltage at the collector of the PNP should rise
>> to >4 volts - if it does and does not when connected, the mosfet has
>> already encountered static.
>
>** 7. I get about 1.88volts. Interestingly the Light dimmly lights up
>untill I put my probe on the gate. I also tried to test the mosfet
>using the following ...
>
Well that 1.88 should be greater than 4 volts up to a maximum of
around 7 volts.

With the gate of the mosfet floating in air it is a very high
impedance (very sensitive to voltage) input and will pick up stray
radio waves and power line frequency floating in the air (especially
with a test lead on it) and that will cause the lamp to come on and
off too rapidly to see and you see it glow dim.

>http://www.uoguelph.ca/~antoon/gadgets/mostest.htm
>It seems to test ok.
>
>Im sorry to be such a dolt on this. Its a simple circuit and yet there
>is something Ive done that just isnt right. By the way on my original
>schematic I put in the orientation of the transistor and Triac are
>they right?
I assume they are right that's how mine are based (some manufacturers
can vary the basing and still give them the same part number but that
is very rare) - the other convention for that style transistor is
E-C-B (but if it already checked in your meter with a gain of 189 -
you had it plugged into the meter with the correct orientation (!)
The meter test also checks the gender of the transistor in case a NPN
snuck into your parts bin. (both of these things you should be in the
habit of checking - gender and base connections when using a
transistor tester, just in case)

>eg Transistor 2N3906 Holding legs from bottom legs pointing down,
>looking at flat part of TR. with round part at the back EBC
> Mosfet IRFZ34 Holding legs from bottom Looking at "front" of mosfet
>Heatsink to top
>GDS.

Yes that's right. Without the four volts necessary to start the
mosfet conducting the circuit cannot work - so that's what you have to
get working - the PNP transistor should be supplying that voltage.

Once that emitter (that has no problem charging to 14 volts with the
transistor out) exceeds the base voltage by point six volts - that
should put about 4-7 volts on the collector (the two 100 K resistors
are a voltage divider that won't allow the voltage to get higher than
7 volts - but at 4 volts it should start flashing already.)

>I have replaced the Mosfet and as I mentioned above exchanged the
>transistor, tested all resistors to make sure they are the right R
>value.
>I even am using a different DC adapter. instead of 12v 300 mA Im now
>using a 12v 800mA thinking maybe there just was not enough current. No
>real change. I have hooked it up in the following way, Using two
>diffierent lights. One is a test light that works up to 50v and the
>other a 12volt car test light. Both work out of the circuit.
>
>Negative ----- Circuit --- Lamp ---- Positive

One caveat with DC adapters - they don't always contain filter caps so
the DC voltage could have a lot of ripple on it. I don't see how the
circuit should be sensitive to ripple, other than throwing the timing
off maybe, but I use a variable 1.2-18 V regulated supply on my test
bench and battery on the bike. A large cap between the plus and minus
output of the adapter should suffice if you have ripple (2,000 uf
16-25 volts or so)
>
>>
>> If the voltage is <4 V at the collector of the PNP with the gate
>> disconnected (and the 100 K is indeed 100 K) the problem is before the
>> mosfet.
>Im not sure what is considered before the mosfet.
>
The circuit as it is before the mosfet (to the left of the mosfet)
that should be providing 4 volts of drive and is not.

Mosfet specs contain something called the "threshold" voltage - that
is the voltage (source to gate) that the mosfet begins conduction at.
Most standard high current mosfets work at about 4 volts - "logic
level" mosfets kick in at ~2 volts.

>Or do you think the mosfet specs I used are Ok. Im not sure where to
>look next.
>Again it is probably user error but I seem blind to what it is. Could
>some of the resistors be lowered to increase power ??
>
>Regards

Concentrate on the base voltage of the PNP transistor - that is
obviously wrong even with the transistor out of the circuit. It could
be wrong because the zener is not a 3.4 volt one, or is connected
backwards (which should give you point six volts not 1.88 like you
write), or the zener is leaky (in which case using a lower value
resistor will hit it with more current - try something much lower like
1-10 K - the thing should work). (if you go much lower the leds could
ghost "on" during the off cycle - only downside, short of burning up
the zener with too much power dissipation - most zeners are 1/2-1 watt
in small diode packages - so you'd be a long way from burning one out)

!%$#&&^#@ Damn! 1N4744?????!!!!! That's a 15 Volt zener diode it
should be a 3.4 Volt zener diode. for this to work it has to be a
much lower voltage like 3.3 or 3.6 Vz diode like a 1N4728 or so.

I can state with certainty that it won't work with a 1N4744 - so your
options are use a 1N4728 or go up to the post where I suggest using a
resistance divider to get ~3.3 volts or string of 6 silicon diodes for
3.6 volts.

In spite of that - I think your base voltage should have been much
higher with a 15 volt diode in there and the transistor out of the
circuit (like whatever your adapter puts out with no zener to limit
it) so something may still be wrong - but start with the right diode
and check it again. Anode to ground side, cathode to 220K (with the
transistor out of the circuit those are the only connections -220K to
+ (lamp to be flashed) , other side of 220K to zener, zener to ground
- NO OTHER CONNECTIONS until the base of the transistor is connected
and it is in a working configuration.

Take care
bob
--