I have a friend that has a motorcycle. He has added a side car onto it. Because of this he has added more lamps onto his motorcycle. To reduce the electricity used by all the extra lamps he has replaced his signal lamps with led signal lamps. They are several LEDs put in a lamp package with socket.
However when he signals the lamps turn on but dont flash. Im guessing that the flashing unit is not drawing enough power to turn off and on.
Can anyone give me a solution to this. I have some small expereince with hobby electronics. Bulding and repairing basic electronic devices. I believe you can buy a device to fix this but thought it would be fun to solve it myself by building something.
The easiest (and maybe coolest) solution might be to add a lot more LEDs to draw about the same current as the incandescent lamp. Now those will be some bright blinkers! I'm not sure how much effect the inrush current of incandescent lamps has on the thermal blinker. Maybe you can add a capacitor across the LEDs?
I can post what I made for my bike only 2 transistors and works over a range of few hundred milliamps to 20 amps.
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I hoped I had, if someone asked. But I do sometimes miss messages or, having seen them perhaps, forget to respond.
Here's the link, in general:
formatting link
And here is the actual ZIP file with the .COM and .SYM files:
formatting link
Just place them together in the same directory and have that directory in your PATH variable. It's a DOS program. There is an option that works under the Win3.1 through WinME operating systems (and I seem to recall that it worked under Win2k) which copies directly to the clipboard. However... it doesn't appear that the method I used works under WinXP. So that is a pain and I need to research how to access the clipboard from a DOS box under WinNT.
I may move this over to a VB program or else a VC++. I just haven't bothered, yet, as the tool is fine for my own use as it is and I haven't had anyone letting me know they use it. So no motivation, as yet.
The library file (ASC.SYM) that is included is easy to edit with any standard ascii file editor, but frankly cryptic and terse. I can explain it easily enough and it isn't hard to work with, if anyone has a mind to expand it further. (I could use help with that.) Symbols that are NOT found in ASC.SYM are not translated and just show up as "holes" in the schematic. When I'm working with schematics and find that I'm missing an entry, I just pop up the .SYM file and paste in a few ascii lines of what I'd like to see and then rerun the program.
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Figure 1: Electronic Auto/Motorcycle turn signal flasher suitable for low current LED signal lamps or incandescent lamps. 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).
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I tried a lot of alternatives before I hit on this one.
First was a trip to the auto parts store - they wanted 8.99 USD for it and through the smoked cover I could see one three terminal device, large cap and a RELAY.
With my immense ego - I figured with a six pack of good beer and some quality time tinkering I could do it with the parts from my junk drawer (room).
I designed four turn signal flashers when I got back home and went through a case of beer. first off was a 555 timer working a relay then mosfet, then an Eccles Jordan multivibrator driving a 600 ohm relay and switching 8 amps max, and a flashing red 5V led switching an NPN bipolar - all required a rather large cap to hold up the supply voltage while the silly thing shorted its own power supply.
Finally I hit on the mosfet. Q1 is a little unconventional with the bias - but since there isn't any significant current requirement for mosfets it works fine (fact is if you leave out the gate discharge resistor (100K) it takes too long to discharge the 10 uf cap)
All told a very nice day tinkering and drinking good beer - and I guess it finally cost me ~15 USD to replace the $9 store bought flasher - but mine has no contacts to wear out or relay armature to adjust and I got a day's entertainment doing what I love.
In balance, an excellent day. Vivaldi on the stereo, good beer, quiet time. Life isn't about electronics after all.
The 3.2 V zener can be replaced with a series string of 5 forward biased signal or rectifier diodes. or a couple of fwd biased LEDs.
You might even use a power NPN transistor in place of the mosfet but the 10 uf cap might have to be larger and the 100 K would be unnecessary. Just a thought - haven't tried it but it should oscillate (fast).
This thing has been in my motorcycle for two years now and works great.
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By the way, here is what the program I have generates from one version I drew up in LTSpice:
That's all automatic. Mosfet looks a little 'flat' I suppose. But that's the size it has to have in ascii to fit with the space allotments made by LTSpice.
Of course, now that I'm thinking about that... why not just remove the diode? I forgot that it shows up only along one branch from the supply and had imagined earlier that it was there to be a protection against reversal. But I think your description is fine, just that the diode may not be required. Why did you add it?
The cap is discharging while the mosfet is in the conducting state (shorting its power source). Q one's bias is "on," with its base close to zero and emitter positive. Resistor is also discharging the gate of the mosfet's capacitance.
The signal diode is there to remove the discharge path through the shorted power source - the objective isn't to discharge the cap rapidly - that's what is holding the gate of the mosfet up and keeping the signal lamp on.
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The diode isn't "necessary" but is slows the discharge of the cap and decreases the size cap required.
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