I'm looking into how to detect the current taken by trailer lights. I came across a combination stop/tail/indicator/reverse light that had an interesting design. The light had a single switch mode supply, run from any of the inputs, to give a regulated 8 V or so, for any input voltage 10 - 30 V. The different colour LEDs were enabled by the individual input voltages.
The point of interest is that all the current is taken by the supply with the largest voltage. So the tail light takes 20 - 30 mA on 12 V, but if the indicator signal goes to 11 V or so, just about no current is taken by the indicator wire, and the tail light wire current jumps to 100 mA or so. The tail light stays at constant brightness, but the indicator comes on, enabled by the indicator wire, but powered by the tail light wire.
My problem is that the light has been mislaid and I can't find where to get lights like that from, to do more testing.
I did find the Ring RCV4800 which does something similar, but only with the tail and brake lights, which are the same LEDs. The LED are lit at a low current by the tail light wire, and the same LED come on brighter if the brake light wire is above about 8 V, but just about all of the current comes from whichever wire is at a higher voltage.
I've tried a few different ones. The cheap 12 V / 24 V ones from ebay don't work on 24 V, for a variety of different reasons.
Has anyone any experience or suggestions where I could get some of these interesting lights from.
The point of interest is that all the current is taken by the supply with the largest voltage. So the tail light takes 20 - 30 mA on 12 V, but if the indicator signal goes to 11 V or so, just about no current is taken by the indicator wire, and the tail light wire current jumps to 100 mA or so. The tail light stays at constant brightness, but the indicator comes on, enabled by the indicator wire, but powered by the tail light wire.
My problem is that the light has been mislaid and I can't find where to get lights like that from, to do more testing.
I did find the Ring RCV4800 which does something similar, but only with the tail and brake lights, which are the same LEDs. The LED are lit at a low current by the tail light wire, and the same LED come on brighter if the brake light wire is above about 8 V, but just about all of the current comes from whichever wire is at a higher voltage.
I've tried a few different ones. The cheap 12 V / 24 V ones from ebay don't work on 24 V, for a variety of different reasons.
Has anyone any experience or suggestions where I could get some of these interesting lights from.
