please help this newbie regarding switching with a wireless remote

[twofake]

Hello,
I have been working on a project using a wireless remote and receiver board. The board outputs DC 5 Volts when toggling from zero volts when a remote button is pressed on and then pressed off. I am using a LM7805 to make sure the voltage to the wireless receiver is kept to 5 VDC.

I initially took the output from the wireless receiver and fed this to the collector of a BC548 transistor (emitter connected to ground and Collector connected to a relay coil). The other side of the relay coil connected to 12 V positive.
This would control the relay. Unfortunately i was using a mini relay and the relay contacts were not great so this idea is not working well.

Aim:
I need to switch 12 V DC power from one PWM current limiting board to a different PWM current limiting board and the current draw of one board is about 470 mA and the other board is about 30 mA.
Can someone please tell me if I can use a cheap and commonly found device like a triac to avoid the use of the relay as i have a lack of space to mount this as well?
Can i use a BT136-600E Through Hole Sensitive Gate Triac and if so, can someone please show me a circuit to use?
The PWM is Dc-Dc adjustable power supply module High-power LED constant current drive that i bought off ebay. I want to toggle between two settings (one limited at 470 mA and one limited at 30 mA but i did try toggling just the current limiting potentiometer and this was not successful as the resistance on the relay contacts made it very inaccurate and there were fluctuating current readings). I now am toggling between one whole Dc-Dc adjustable power supply module High-power LED constant current drive to the other whole Dc-Dc adjustable power supply module High-power LED constant current drive.
The power i am using is a Lithium battery pack so the wireless remote circuit sits inside the battery pack (as well as the two Dc-Dc adjustable power supply module High-power LED constant current drive boards) so that is why i have limited room for the Triacs or whatever you suggest.
Many thanks in advance.

 

[alec_t]

Providing you can use low-side switching I would suggest two modern logic-level N-channel MOSFETs rated for Rds(on) < 100mΩ and Vd > 30V, plus some logic to ensure one is on and the other is off.

 

[twofake]

Providing you can use low-side switching I would suggest two modern logic-level N-channel MOSFETs rated for Rds(on) < 100mΩ and Vd > 30V, plus some logic to ensure one is on and the other is off.

Thanks alec_t. I looked up what you suggested and they look like what i need. How can i set it up so that zero volts switches on one PWM board and 5 V switches to the other PWM board without relays? Any suggestions?

 

[alec_t]

You could try this:

 

[twofake]

Thanks. That circuit looks brilliant. Sorry about the newbie question but what are M1 and M2 and can the N MOSFET in this circuit be changed with an IRF Z44N with some other component changes of course ( because , after hearing about N MOSFETs I just bought ten of them to experiment with.

 

[alec_t]

M1 and M2 are N MOSFETs, which need to be "logic-level" types as I said in post #2, so that they switch on fully with a gate voltage < 5V.
Unfortunately the IRFZ44N isn't that type. Its turn-on voltage is 4V; which means that it is only just beginning to turn partly on with a 4V gate voltage and would need ~10V to switch on fully. Try searching your electronics component supplier's website for 'logic level n mosfet'.

 

[twofake]

Many thanks again . Looks like I will doing some more research . The N MOSFETs I have already bought will come in handy for electronics testing and experiments .