richs09 posted:Rod -- nice job -- this might be what I've been looking for -- so a coupla questions: I am currently running variable AC track power for my American Flyer/Flyonel, etc. I've been wanting to replace the lighting in my passenger cars and cabeese using the LED strips, which run at ~12V DC and came to the conclusion I'd need to have a buck-boost circuit to provide power to the lights to account for the time when the AC track voltage was less than 12V. I assume your circuit is a buck system, so at track voltages less than 12V AC, the output DC voltage would be less than that - presumably at whatever voltage the regulator is set for? If the input voltage goes below the regulator set point, then I gather the output DC voltage is zero?
Assuming your board would work in my case, then I have two operational questions: first, you say that the board should have an isolated ground. In my case, most/all of my passenger cars and cabeese are grounded through the metal chassis, so the current light bulb circuit is grounded through the connection between the outside shell of the light bulb socket and the metal chassis (which is then connected to the truck and metal wheels to the "base" rail). I assume this all means that I need to isolate the ground side of the 12V DC so that the only ground connection is between the LED strip and the ground side of the output on the board. Second, you mention that the voltage regulator chip gets hot, so one needs to keep it away from anything plastic. Almost all of my passenger cars have plastic shells. If the board were mounted to the chassis so that all the components are "in the air" is that sufficient? Does the regulator get as hot as the incandescent bulb that would be replaced by all this?
thanks,
Rich
Rich, I think for your application you should be considering the DIY constant current led lighting board, which is linked also in this thread. Link here: https://ogrforum.ogaugerr.com/...ighting-module-files
This is a very similar board, exactly the same number of components, and the same size. The difference is it controls current, not voltage, and is specifically intended for led strip lighting of passenger cars.
Yes the only connection to the outputs of the board should be to the led strip.
Lighting an led strip should not take more than 50 ma or so, and the regulator gets warm to the touch, but not super hot. In my testing at up to 100 ma using track voltage of 18vac, I did not see higher than 72C on the reg. I have used these guys in quite a few plastic body passenger cars without heat sinking. You just have to keep the reg tab away from any close plastic.
If you decide to mount the reg to the chassis plate for cooling you just need to be sure that the tab is insulated by a silicon pad and the mounting stud is also insulated. The tab must not make electrical contact with the base plate. Nothing else on the board generates any heat.
Note that depending on what your normal track voltage is will affect your led voltage choice. Standard 12vdc leds are great for command use with a track voltage of 18vac or so. If you are running lower or variable track voltage, 5vdc leds would be a better choice, because they will be fully lit at about 6 vac supply voltage. If you want to use 12vdc leds with low variable power, you need a boost converter, which this is not. Hope that all makes sense.
Rod
