Hello,
Let me first say thanks for such a great collection of electronics information! I have a topic that I couldn't find covered here, regarding powering an accessory when either of two turn-on leads have been energized. Search turned up a topic
here, but it seemed a bit more complex than my scenario with multiple diodes and resistors.
On my 2018 Tundra, I have a pair of Baja Designs accessory LED backup lights ("Squadron Sport": 3,150 lumens, 26 watts @ 2 amps
each). I want them to come on when
either or both of the following events happens:
- Shift truck into Reverse
- Flip accessory switch (in camper shell)
For a turn-on signal for the first event, I have tapped into the Reverse wire going to my trailer harness. For a turn-on signal for the second event, I have a + lead coming from my accessory switch. I then have a ground wire, and a fused power wire, which originate from a fuse distribution block in the bed of my truck. Finally, the LED backup lights present as a single + and - wire; note that the lights indicate they have "Built-In Overvoltage Protection", whatever that means.
To wire this scenario up correctly, can I simply follow the instructions in
1 - Connecting Additional Devices to The Remote Turn On Wire, where:
- Both turn-on leads listed above are joined together and go to terminal #86
- Power wire from fused distribution block goes to terminal #87
- Ground wire from distribution block and LED Backup lights' - wire are joined together and go to terminal #85
- LED Backup lights' + wire goes to terminal #30
Is there any concern about power leaking from one of the turn-on leads, when energized, into the other, and causing problems? Is this an application that calls for a diode, which I've read in a few different posts relating to LED lights?
Thank you for your help!
Use a diode in series with each of your turn on leads (with cathode towards relay coil).
Both diodes will feed the coil of your relay (with the other side of the relay connected to ground).
Use the NO contacts to feed +12V to your LEDs as you described in your post.
eguru] wrote:
se a diode in series...
Thanks for your help! I am new to working with diodes and have enjoyed reading up and learning a bit about them. I could use some advice on whether I've selected the correct one for this application.
Based on the specs of the weather-proof relay I've selected, whose coil is spec'd to a max current of 133 mA +/- 10%, the diode's operating limits in this scenario are a max voltage rating of 37.5v (15v peak output from my alternator, x 2.5 fudge factor) and a max current of 368 mA (133mA + 10% max current per spec, x 2.5 fudge factor).
I've selected this diode:
1A 36VDC diode
It states it's a "1A diode" which I assume is its DC forward current rating which is well within the 368mA max, and that it's rated to 36VDC which is close enough to my 37.5v max voltage output. (If my alternator truly puts out 37.5v I have bigger problems than a blown 39 cent diode).
The link doesn't provide detail on the actual part number. Just get any of 1N4002, 1N4003, 1N4004, 1n4005, 1N4006, or 1N4007.
Those part numbers are inexpensive and easy to source.