R1 = 10K, 1/2W C1 = 0.1uF/50V, ceramic
R2 = 220 C2 = 47uF/25V, electrolytic
R3 = 250K D1,D2 = 1N4005
Q1 = IRFZ44 MOSFET Led1 = High Brightness, color of your choice
U1 = MC14049 CMOS
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[Motorcycle Turn Signal KIT]
This circuit is based on the CMOS IC from Motorola, the MC14049UB Hex Inverting Buffer. Of course, the regular CD4049
can be used and is pin-for-pin compatible. The 4049 is a 16-pin chip. Maximum DC supply voltage should not exceed
18V. The above diagram can replace your existing mechanical clicker. The prototype worked excellently!
When the turn-signal system is first turned on, either diode D1 or D2 blocks current from going to both lamps at the
U1-a and U1-b control the signal duration, which timing is set with the electrolytic capacitor C2 (47uF)
and R3. Turn-signal duration can be adjusted with the 200K trimmer pot R3. This signal is then fed, via the
U1-c buffer to MOSFET transistor Q1, which in turn provides enough power for driving the turn signal lamps.
The other buffers drive the 'Indicator' Led1. Buffers U1-e and U1-f can drive 3.2mA each so three are
needed. Current through the Led1 is limited with R2, 220 ohm.
MOSFET transistor Q1 can be substituted for many types, it is not critical. I used the IRF513 because I had it
available at the time. The NTE66 is a direct replacement and works great too. I experimented with other types
(IRF511, IRF512, IRFZ42, IRFZ44 etc) and they all worked satisfactory. The prototype uses the IRFZ44 and functions
For trimmer pot R3, if you don't have 200K, use 250K or 300K. They will all work but the excess resistance is a bit
overkill. The 200K is more than enough. C1 can be any type as long as the working voltage is 50V or more. Foil
types work very well but a ceramic model can be used also.
Switch S1 is your existing turn-signal switch. You can simply take the old mechanical unit out and replace it
with this electronic version.
The Printed Circuit Board and Lay-out are listed below. Note that the pcb is *NOT* included in the kit.
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Page copyright © 2008, Tony van Roon.
Original author unknown. Modifications, PCB & Lay-out (C) by Tony van Roon.