LED traffic light power question

[Splint3048]

Hi,

I'm new to this forum and come from a mechanical engineering/motor mechanic background, so the question I'm about to ask is pretty basic.

I have an Aldridge traffic light which I intend running with a 12V battery, but I powered the array directly via the red an black wires, bypassing the AC to DC circuit and the jumper wire (red one on the bottom image) got very hot, very quickly. The jumper wire is clearly a smaller gage wire but I did not expect it to get so hot so quickly.

I've been doing a bit if research on this and it seems like I should be running a current limiting resistor but there are resistors built in (see image) so I assume they are the resistors.

Can anyone tell me what's going on with it and what I need to do to run it without damaging it?

Thanks

 

[Harald Kapp]

I powered the array directly via the red an black wires, bypassing the AC to DC circuit

By directly connecting a voltage source to the red and black wires you not only bypassed the AC/DC circuit but also the current controlling circuit.
LEDs need a controlled current, generally you can't power them directly from a voltage source.

Try using the AC input instead and connect the battery to the pins labeled AC. It looks like there is no transformer involved, all the AC/DC conversion is done by semiconductors. These will usually be happy to accept a DC input, too. From there on the rest of the circuit will do all the conditioning to power the LEDs correctly.

 

[Alec_t]

I've been doing a bit if research on this and it seems like I should be running a current limiting resistor

That is certainly true for simple LED arrays, but what you have is far more complex and hopefully that circuit board should provide any necessary current limiting. If it doesn't, the board could be expecting to be powered by a constant-current source. What do the instructions for it say?

 

[Splint3048]

Try using the AC input instead and connect the battery to the pins labeled AC.

Thanks. Just tried it and it seems to work fine. I appreciate your feedback.

 

[AnalogKid]

Don't know why there are *two* axial components per LED, but it looks like there is current limiting per LED built into the board. Dan you give us the component values?

The numbers work out to around 6 mA per LED. That seems low to me, even for a high-reliability device.

Also, that controller has a *lot* of parts, especially if it is a single-output supply with remote sense. Please identify the two 14-pin IC's. And, is the top-left big yellow box a relay or a capacitor?

ak