• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Help!!!!!, Relay in motorcycle 12V environment,

Not open for further replies.


New Member

I was hoping some can help me figure if i can use SRD-12VDC-SL-C, to turn may parking light into blinkers.

Here is the issue;
I purchased aftermarket blinkers for my motorcycle, these only light up while blinkers are turn on, making you less visible during regular operation.
Hence, OEM have "daylight running lights/parking lights" and additional filament for blinkers. So I have single negative wire, 12V always on (while motorcycle is operating of course) and another 12V wire for operation of blinkers.

What I'm considering is;
Wire relays "normally on" leads with 12v parking lights, that will provide me with set of running lights and wire relays coil leads with 12V blinker switched.
This should give me always on running/parking lights that will turn off and on while I hit the blinker.

My question is;
I know car relays have build in resistor or diodes to prevent return voltage spike, and damaging onboard computers, displays and low voltage transistors.
SRD-12VDC-SL-C does not have build in resistor. Do I add resistor within relay circuit and that will be fine? Should I get new relay with resistors build in?

If I was to add resistor, what type, voltage, ohms resistor do I need to use?
I should add, if it makes no difference between two types or relays I mentioned above, I would like to use SRD-12VDC-SL-C because of how small they are.

Any help or opinions deeply appreciated.




New Member
Thank you so much for replying,

I'm really bad at this and its not my place of any expertise.

Is there anything else I can provide you with to help me pick correct resistor?

Thx in advance.

Should I just order these and these will be fine:

See 6. COIL DATA CHART (AT20 C) -- your coil inductance may be around 350mH to 900mH , it's Power.I/O 360mW or 450mW -- is the minimum half- or quarter-value for suppressor components e.g 1W to 2W resistor - depending on circuit . . .
general -- http://www.electronics-tutorials.ws/io/io_5.html
Not open for further replies.

EE World Online Articles