Solid State Micro Relay Application

Electromechanical Relays
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1

I have an application for an electric construction vehicle to flash blue lights to let people know it is approaching as it can be nearly silent.
JW SPEAKER has supplied the LED “Blue Lights” and we currently flash them on and off using a Song Chuan relay (871-1C-C-R1-U01-12VDC). The problem is the unit is so quiet that the clicking relay annoys the user in the cab so a solid state micro relay is needed to eliminate the clicking of the relay as the lights are flashed on and off. I tried an ETA brand ESR10-NC2A4HB-00-D1-17A. The lights briefly came on once and never came on again. Any one have any ideas? Needs to be 12VDC and “Micro” relay format to fit in existing production FRC. Thanks!

2

sosman,

Since the ETA brand relay only worked briefly I am left to wonder if the current draw from the lights was higher than what the part could handle. Do you know the draw of the LED lights when they are on?

3

I will get a handle on that and let you know.

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4

It appears that the blue lights draw 0.46 Amps each. So for the 6 lights ( 2 headlights, 2 tail lights, 2 side lights ) it would be a total draw of 2.76 Amps ( 6 x 046 ). Thanks!

5

Correction: 6 x 0.46 = 2.76 Amps.

6

That’s nowhere near the limit of that relay, so that shouldn’t be the problem. I can think of three possible issues to check.

  1. Unlike a mechanical relay, all of the contacts are polarity sensitive, and reversing polarity on any of them would cause malfunction.
  2. The load must be placed between pin 5 (the center tab) and ground. The load can not be placed between the 12V battery and pin 3 (the top tab).
  3. Because the relay control input (pin 1) will only draw about 10mA rather than around 100mA when turned on (as would be the case for a relay coil), some systems might interpret that as a faulty condition and automatically turn it off.

Here is the proper way to wire your circuit. Note the polarity of each contact and the position of the load between pin 5 and ground.

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7

I finally got back to this problem. Of the three possible issues to check you listed for me it was number 3. If I add a 120 ohm 1 watt resistor across pins 1 and 2 ( the input ) it works. So each unit does not have to be modified in this manner I am asking the Software Engineer to lower the fault detection range in the controller for that relay. I really appreciate your help on the manner! Thanks!

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8

Glad it seems to be working. Let us know how it works out.