Motorcycle flasher problem.

[steve]

PS.

Sadly I don't use a news transport because my ISP (one of the Biggest
in the region if not country ~ Rogers) stopped providing news feeds to
its valued customers, so I'm relegated to Google Groups. However if
you search in Google / Google Groups and go to sci.electronics.basics
you can see our posts and the schematics. Albiet the past ones I don't
think worked (sorry abou that) but the last two I tested first on a
test group then once posted I copied from Google Groups and pasted
into notepad with terminal font and they seemed to work fine now.

Steve

 

[Randy Day]

I see what you mean on the ascii drawings I tried to copy my own from
my post and it didnt work. I think I know why.

Here they are again. Now copy and put in notepad.

Mosfet Removed

First off, the zener on the right hand side
is the wrong value. You don't need a zener
there at all until you put the mosfet back in.

Replace it with a 15v zener, not a 3.3; that's
why the light is always on, and one reason why
the rest doesn't work.

 

[steve]

Just for clarity, your saying that I should use the Zener 16v Diode,
1N4744. As spec'ed in the original Schematic, from + --|<-- -

Regards

 

[default]

I see what you mean on the ascii drawings I tried to copy my own from
my post and it didnt work. I think I know why.

Here they are again. Now copy and put in notepad.

Mosfet Removed


+o-------,
| + o
Diode1N4148 (2.93) | | /
.------------.-|<-.----o--------o---. |Lamp
| Anode | | .-. /
| . - . | | ( X )- ---
| .------. | | '-' \
o | T R | | | | \
| |2n3906| o | o
|(2.72v) '------' | | |
.-. | | | .-. | |
| | 100k | | | | | 220k | |
| | E B C | | | |
'-' '-' | |
|(2.69v) | | |
o-----. o | |
| | TR 2N3906 | | |
| | | |
| [Emitter Removed] | | '--.
| | E |(.86) | |
| (Q1)>| (.86v) | |3.3 |
| |-----B--------o |1N4728|
| + /| | |Zener |
--- | C | | |
--- | | /--/ |
10uf |(0v) | 10k | Collector ^ |
/16v | '----|___|-------|----Removed |0v |
Elec | | (open) | |
trol | | | |
ytic | 3.3Vz | | |
| 1N4728 /--/ | o--'
| Zener ^ | +
| |(0v |
o----------------------o----o---o---'
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

That's a vast improvement in the schematic.

AND with nothing but the 3 volt zener in the schematic you should be
getting just what you are getting.

The lamp provides a path to the zener. With 14 volts more or less
going into the lamp the zener breaks down and conducts (as intended)
causing the lamp to light with about 11 volts on it and 3 volts on the
circuit.

That is the zener that should be a 15++ volt type - that is only
there so the vehicles electrical system can't destroy the mosfet with
a high voltage spike - otherwise it serves no function. But a 3 Vz
diode there is entirely wrong so remove it. Lamp should not turn on.

While it is out. Measure voltages. (PNP with emitter and collector
disconnected as shown)

You should have something like 14 volts at the 1N4148 where you now
show ~3 volts. Then Measure at the 3.3 Vz diode cathode and it should
be 3.3 volts or close.

All that does is determine that the 3 volt reference is working as it
should. If it doesn't work that has to be fixed.

If it does give three volts, connect the emitter and measure the
collector with it disconnected from anything. The emitter should be
over 4 volts and collector ditto.

Don't go further until that voltage is there, that has to be working
before anything else will work.

Then the mosfet goes back in but leave the gate disconnected and the
lamp should be off/out. Leave it on awhile if the lamp is lit and see
if it goes out. With a floating gate - it may go off as the gate
charge bleeds off.

If it stays on it may still be OK. With the drain connected to the
lamp, source connected to ground (just like the circuit) and gate
connected to the source via the 100K resistor (again just like the
circuit) it should go out. The 100K should be more than ample to
bleed off any gate charge quickly.

Right now your schematic doesn't show a 100K

The 10 K off the collector should work but I think I used a 1K in my
original design - that is another part that isn't really needed and
just serves to buffer the gate of the mosfet from spikes.

If all that works as anticipated there's just connecting the gate to
the collector via the 10-1 K and see what happens.

I'd use some incandescent lamp load until we get it working since too
low a load may cause the working voltages to be too low. In your bike
you'll undoubtedly have more load. Just trying to control the
variables here to aid in troubleshooting . . .

good luck
bob
--

 

[gearhead]

Hey, Steve, I've done something similar on my 2004 Honda Sabre.
I use a LM555 timer chip
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
--HC

You can get any duty cycle you want. Put a diode in parallel with the
resistor between pin 7 and pin 6. Point the cathode (stripe) toward
pin 6.

 

[HC]

You can get any duty cycle you want. Put a diode in parallel with the
resistor between pin 7 and pin 6. Point the cathode (stripe) toward
pin 6.

Hey, Gearhead, thank you for your reply. I did a LITTLE messing
around with a diode (1N4001) between pins 7 and 6 and that was cool.
I'll play with it more later but good suggestion, thank you. What I
was intending to convey in my response earlier was that, if I
understand the application notes from National Semiconductor the
oscillations of the 555 are limited to 50% and then I wanted to convey
that if the SOURCE at 50% or less was not enough that the OP could use
the DRAIN at more than 50% to run their application. I did not intend
to infer that a driven circuit from the 555 could not be run at 50% or
less only (as I have used the negative pulse to sink voltage from a
relay to get the higher-than-50% output. I'm sorry if I appeared
misleading and did not intend to. Thank you for your suggestion
because I would love a way to get a longer HIGH output from the 555.

--HC