RCA plug connection from 12V battery to dew heater controller - Page 1
Forum section: electronics / beginners

author: Circuitous3
author_rank: Contributor
timestamp: April 05, 2023, 01:26:34 am
content: I am building a dew heater system for dew control on my telescope. The system consists of a dew heater controller which supplies power from a 12V lead-acid battery to up to 4 nichrome wire heater elements which heat various accessories on the telescope to prevent dew formation. The heater elements plug into the jacks located on the sides of the controller box. The main power supply is through wires from the battery to the same male RCA plug as used for the heater elements. See attached pictures. As I'm nearing completion of the project, I realized that my choice of a male plug is not commonly used. I have seen female plugs used to supply power to telescopes for other purposes, or a permanent connection via a cable gland to the front of the controller. But I chose the detachable male plug, which attaches to the jack on the front of the box, for ease of use. The voltage to the heater elements is controlled by pulse width modulators and will carry a maximum current of 0.4 amp. The plug is rated for 2.0 amps. Do you see any issues with supplying power to the controller via the male plug?

author: Whales
author_rank: Super Contributor
timestamp: April 05, 2023, 01:44:11 am
content: I'd say you did this the right way around. The male plug can easily be shorted out if placed near a metal surface, but the female plug can't, so it makes sense for the female to be the power supply side.EDIT: ah I think you're also asking about how you supply power to the controller box itself? Yes you should do it the other way around to avoid the shorting problem I mention above. Or use a DC barrel jack (you can get round panel-mount versions that are easy to drill a hole for and then install).It's unusual to use RCA conns at this current level, but it looks like you are making your own cables so this is OK. I wouldn't trust TV RCA cables to have enough copper in them.Other options of note include:- M12 connectors. Round (so you can easily drill round holes in your cases) and come in different pin counts.- Bananas jacks. Round. Polarity doesn't matter for heaters.

author: Circuitous3
author_rank: Contributor
timestamp: April 05, 2023, 02:22:06 am
content: Thank you for this information Whales. Yes, I take your point about the possibility of shorting. Given the amount of work involved already, I'd like to test the system as is to see if it works as planned, and make the male-to-female plug change for the input power supply down the road. When you say that it's unusual to use RCA connections at this current level, do you mean at such a relatively low current level? Other than the potential shorting problem, which I'll be careful to avoid, do you see any other major issues with supplying power from a 12V battery to the controller box RCA jack via the plug connector?

author: Circuitous3
author_rank: Contributor
timestamp: April 05, 2023, 02:38:05 am
content: Are you referring to these types of connectors? Thank you,https://www.amazon.in/Female-Panel-Mount-Power-Connector/dp/B07PFWQ1RJ

author: Whales
author_rank: Super Contributor
timestamp: April 05, 2023, 04:25:01 am
content: QuoteNo, the other way around.I've only ever seen RCA connectors and cables being used for signals (not power) such as audio, composite video and component video. Quick approximate calculation: 75ohm termination resistor, 1V signal level -> 14mA current. For signals like these the DC resistance of the cable doesn't matter too much either (it's OK if 20% or maybe even more of that voltage is lost).QuoteThat item shows PCB-mount female jacks. If you're not using a PCB then something like these panel-mount/case-mount versions will be easier:https://www.lcsc.com/product-detail/AC-DC-Power-Connectors_XKB-Connectivity-DC-022B-2-0_C319097.htmlhttps://www.lcsc.com/product-detail/AC-DC-Power-Connectors_XKB-Connectivity-DC-025LM-5A-2-0_C381107.htmlNote the two types. One is inserted from outside of the case (and then soldered), the other is inserted from inside the case (so you can solder it before or after). I much prefer the latter.Also be wary of the centre post diameter. 2.0mm, 2.1mm and 2.5mm are the most common. Sometimes 2.0 and 2.1 fit each other, but it's best not to rely on it.

author: Whales
author_rank: Super Contributor
timestamp: April 05, 2023, 04:30:04 am
content: For "M12" connectors I mean something like this:https://www.lcsc.com/product-detail/Circular-Connectors-Cable-Connectors_Liansheng-HKT-00006_C2876034.htmlhttps://www.lcsc.com/product-detail/Circular-Connectors-Cable-Connectors_TXGA-FM16-04MS001_C2834295.htmlMany soldering iron stations use something similar (different pincount & possibly diam?)