Wiring lights a little differently

[monkeyracing]

I was playing with the lighting setup for the CC-01 today and noticed that it was taking battery voltage and stepping it up to 9v at the output side. I also noticed the lighting controller is kind of big for running 2 sets of lights. It's the TLU-01, with 8 channels out and a controller input of some kind.

I saw a video a few days back (wish I'd bookmarked it) of a guy who set up a rig where had a 9v battery stuck to the chassis of his crawler. He ran the wires from that to the body posts where they were attached to 2 washers. On the body, the lights were mounted as normal, but connected to a matching pair of washers, so when the body was attached, the washers contacted and power got through to the LEDs.

What I'm trying to figure out is A) Where the hell dd I see this video? and B) How has Tamiya set it up so 2 red LEDs in series can handle 9 volts? Reds are usually about 1.5v each and with 2 in series, 3v. Haven't seen a resistor anywhere on the lights or in their wiring. That extra 6v should have them dying in about 30 seconds.

Jim

[wantAsummit]

Did you measure the voltage with the LEDs connected?

[AreCee]

The resistors are built into their control box. Measure the voltages at each socket and they will be much lower than 9V.

[monkeyracing]

Nope. Measured at each socket and they all came up at 9v. There are a boatload of SMT resistors on the PCB. I think they probably have more to do with advanced functions than voltage regulation though.

Here's the weird part. I was playing with the red LEDs and figured if they function okay on the 9v from the controller, they'd be fine with 8v from a battery. Nope. One flash and they were done.

I suspect the lighting control unit is supplying the 9v, but pulsed. Like power is only applied 50% of the time. This is done on automotives a lot. Interesting. Wish I had an oscilloscope.


Jim

[wantAsummit]

Again, did you measure the voltage with the LEDs hooked up?

[monkeyracing]

Nope. Do you suspect the controller adjusts voltage at each socket based on what's plugged in to it? I can't see it, but it's possible.

Think l'll just bust out some 1/4w resistors and do it the old fashioned way.


Jim

[Olle P]

Originally Posted by monkeyracing

... Do you suspect the controller adjusts voltage at each socket based on what's plugged in to it?

Nope, the controller doesn't, but the attached load (normally LEDs) define the voltage and the controller limits the output current.

In an (almost) open circuit, like the one you measured, the controller tries its very best to push the right current through your voltmeter. It'can't go higher than those 9V to do it though...

[Charlie-III]

Originally Posted by Olle P

Nope, the controller doesn't, but the attached load (normally LEDs) define the voltage and the controller limits the output current.

In an (almost) open circuit, like the one you measured, the controller tries its very best to push the right current through your voltmeter. It'can't go higher than those 9V to do it though...

Nice explanation, thanks for sharing. I don't mess with lights, but may do so while testing a GT3B.

[monkeyracing]

Very interesting. I didn't think a cheap light controller like this would incorporate a current limiting feature. It sounds like the current gets controlled at each socket, as you mentioned, based on input.

I'm setting the controller aside and have built the lighting harnesses with resistors in line. They ideally run on 9v, but will operate down to about 6v.

Who'd have thought something as simple as a few LEDs on a toy car would get so techy?

Now I need to figure out how to warm up the colour on the horrible bright white headlamps...


Jim

[SMR 510RR]

Originally Posted by monkeyracing

Very interesting. I didn't think a cheap light controller like this would incorporate a current limiting feature. It sounds like the current gets controlled at each socket, as you mentioned, based on input.

I'm setting the controller aside and have built the lighting harnesses with resistors in line. They ideally run on 9v, but will operate down to about 6v.

Who'd have thought something as simple as a few LEDs on a toy car would get so techy?

Now I need to figure out how to warm up the colour on the horrible bright white headlamps...


Jim

Why use a 9v battery? Just run it off the 6v powering your RX and plan your resistors accordingly.

[monkeyracing]

Could have done that, but I've got a terrible habit of yanking the body off a chassis with the wires still hooked up. Running 9v is light, cheap, easy and gives me options, like using a regular 9v battery, button cells, etc.


Jim

[Theibault]

I saw the same video. If I recall right, it was in a thread somewhere on Tamiyaclub.com?

[monkeyracing]

I think you're right. Thanks for the reminder.


Jim