So I've been working on a wireless remote relay switch using several components and have struck a break wall. The issue I'm having is that the D0 siginal output triggers the relay but only at short range. When using 2 different power sources the relay behaves as it should with pretty good distance.

Basically the issue I think I'm having is related to a power one which is beyond me and hopefully someone can guide me in the right direction.

Below is the some details of each main component:

  • 315mhz SC2272-M4 Receiver (5v)
  • 315mhz 4-CH SC2262 Transmitter (12v)
  • High & Low Level SRD-05VDC-SL-C Relay circuit for Uno 3 (5v)

Here's what I've tried.


simulate this circuit – Schematic created using CircuitLab

Basically what I'm finding is that D0 is dropping mA and not driving the high level trigger, but it works fine with its own power source, something I hoped to correct by using a 1AMP+ Mains USB supply. Is there a better way to resolve this issue. Oh, I've also messaged the seller of the high low level trigger relays to find out the exact mA at which the low and high triggers trigger on.


As recommended I have tested the circuit with a multimeter and here's what I've discovered.

When activating relay:

  • Data 0 (DCA - 20m) drops from 8.70 to 7.75 (very unstable sometimes can drop as low as 1.0)
  • Data 0 (DCV 5v) drops from 5v to 4.3v (very unstable when range is increased, as low as 0.33v)
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    \$\begingroup\$ What happens if you add a couple capacitors to the circuit? Maybe 100nF in parallel to 10uF close to the receiver and same construction close to the relay circuit? \$\endgroup\$ – jippie Aug 17 '14 at 17:25
  • \$\begingroup\$ I haven't tried that, I have some capacitors on order so hopefully will be able to test by Wednesday. What do you think is happening? \$\endgroup\$ – Simon Hayter Aug 17 '14 at 17:32
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    \$\begingroup\$ I think your power supply briefly drops from the relays being activated, in turn the receiver electronics state get corrupted. \$\endgroup\$ – jippie Aug 17 '14 at 17:34
  • \$\begingroup\$ Ah, I see, its been over 15 years since I did electronics at school and had to refresh myself on the capacitors. So, let's see if I got ya right! Basically when the relay turns on there is a temporary drop in mA. By using some capacitors it'd build up juice and therefor supply the extra boost temporary to avoid the temporary drop? Sorry, if I make no sense lol. \$\endgroup\$ – Simon Hayter Aug 17 '14 at 17:39
  • \$\begingroup\$ It might be worth mentioning its a looping problem I have, the relay clicks on clicks off repadly when using same power source. \$\endgroup\$ – Simon Hayter Aug 17 '14 at 17:40