Mosfet for Turn Signal Relay.

Thread Starter

HexaPro

Joined Aug 21, 2020
3
Hi, I want to use mosfet to replace the relay I use for my motorcycle turn signal light. I use relay to connect directly from the battery so the light can be brighter and lit more stable (not flickering as the engine rotate). So the relay connected to the flasher and the battery. I tried to use a combination of n (IRFZ44NPBF) and p channel enhancement (IRF9540NPBF) mosfet paired with 10K resistor each but the LED stays on and not blinking as it should when I use a relay. Any suggestion what mosfet should I use so it would blink according to the flasher?
 

geekoftheweek

Joined Oct 6, 2013
1,248
My initial thought is you aren't drawing enough current for the flasher to work right. How about a drawing so we all can see just what for sure and how things are connected.
 

Thread Starter

HexaPro

Joined Aug 21, 2020
3
So how do I add more load, what kind of load should I use?
I have tried to replace the automotive relay with SRD-12VDC-SL-C before, and the flasher also not working right, when I rev the engine the LED stays on much longer than it should and only blink briefly.
Should I make my own flasher with no load sensing? How do I do that?
I'm a newbie on electronics, I only know a few basic stuff.
Thank you for the reply.

1606373174431.jpg
 

geekoftheweek

Joined Oct 6, 2013
1,248
You can get dummy load resistors designed for automotive conversion from incandescent to LED lighting online or auto parts stores. If you originally had incandescent lights two of them in parallel would probably be needed, but one may be enough. If LEDs to start with one resistor would probably be more than enough... maybe two in series to start and see how it goes. Place the resistors between the output of the flasher and ground.

Other than that I'm sure there is some sort of 555 timer circuit that could be used, but I've never done anything with them myself.
 

Thread Starter

HexaPro

Joined Aug 21, 2020
3
You can get dummy load resistors designed for automotive conversion from incandescent to LED lighting online or auto parts stores. If you originally had incandescent lights two of them in parallel would probably be needed, but one may be enough. If LEDs to start with one resistor would probably be more than enough... maybe two in series to start and see how it goes. Place the resistors between the output of the flasher and ground.

Other than that I'm sure there is some sort of 555 timer circuit that could be used, but I've never done anything with them myself.
Thank you for the reply.

I'll try to find something as the dummy load, I'll post back the result when I have the time to work on my bike again, perhaps Sunday.
 

geekoftheweek

Joined Oct 6, 2013
1,248
Crutschow made a good point I didn't consider, but the project still sounds cool. If your LED lights are flickering and such with engine speed the minimum voltage for the lights is probably too close to what your alternator puts out. The lights I've messed with will get dimmer under a certain voltage, but above that voltage they are the same brightness no matter the voltage.

Also thought the resistors would be better after the switch. I didn't see it in your schematic and didn't think about it at the time. I'm assuming power goes through the flasher to the turn signal switch which then lights up either side.

Good luck
 
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