High Temp Power indicator (>110C) - Page 1
Forum section: electronics / general

author: Otwin38BOH
author_rank: Newbie
timestamp: March 18, 2022, 10:55:22 am
content: Hi,Has anyone had experience sourcing a power-on indicator that will function in an environment that will be 110-120C?I'm looking for something that would be small & panel mount. LEDs are specifified to 85-100C. Incandescnt bulbs may be an option, but I can't find any temp specs for those that indicate whether they function on that temp range. Obviously oven bulbs function at 300C+, but are much too large for an indicator, but gives hope an incandescent bulb may work.Any feedback on this would be appreciated.Thanks,Kevin

author: richard.cs
author_rank: Super Contributor
timestamp: March 18, 2022, 11:11:39 am
content: Neon lamp?

author: SeanB
author_rank: Super Contributor
timestamp: March 18, 2022, 01:57:13 pm
content: Neon or incandescent lamp, temperature more limited by the holder that you use for them, so you are kind of stuck on using a metal and glass lamp holder for them. No plastic on them, unless you have bakelite, which even then will suffer from degadation with time, thus you need ones with ceramic insulators. normally this is a neon lamp, with associated resistor, which can easily withstand the temperature, though the connections between the lamp, resistor and the wires are going to need to be crimped uninsulated connections, with glass fibre sleeving over them, and high temperature glass fibre sleeved wire to apply power to them.

author: Otwin38BOH
author_rank: Newbie
timestamp: March 18, 2022, 04:00:09 pm
content: Thanks for the replies. I'll look into a neon option, though it seems to be focused on 120V power, where I have 28V DC.I imagine we'll use teflon wires and crimp as much as possible.

author: voltsandjolts
author_rank: Unknown
timestamp: March 18, 2022, 04:42:10 pm
content: LEDs work fine at 150C+Don't worry about specificationsKeep power dissipation as low as practicably possible.For 120C, solder is fine, don't need to use crimps unless you specifically want to.

author: BrokenYugo
author_rank: Super Contributor
timestamp: March 18, 2022, 06:24:21 pm
content: You can't run a neon on 28 volts DC, you need something like like 4 times that to reliably start one.Fiber optic cable and a LED back in the cool zone?

author: Gregg
author_rank: Super Contributor
timestamp: March 18, 2022, 11:52:39 pm
content: Halogen lamps should be available in 24V 10 watt T3 bi-pin connection. If they burn out too quickly a resistor in series could be used for your 28V system. Ceramic lamp sockets should also be readily available. A quick amazon search yielded this:https://www.amazon.com/dp/B00VYV5DII

author: Otwin38BOH
author_rank: Newbie
timestamp: March 29, 2022, 10:01:13 am
content: Thanks for all your feedback.I can make a higher voltage from the 28V (135V DV) to power (half) a neon.I'm trying to keep everything as low power as possible.There is no 'cool zone' in the environment. This is also high vibration, so neon/diodes would be more suitabale for that.I may do some testing on LEDs, but my first test melted the plastic lense.

author: DavidAlfa
author_rank: Super Contributor
timestamp: March 29, 2022, 05:00:02 pm
content: The highest temperature parts are usually rated for 125ºC, so I there must be a colder zone elsewhere for electronics?If so, maybe you could use fiber optics?Otherwise, what kind of electronics are you using? 150ºC rated parts are very rare!

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 29, 2022, 05:40:53 pm
content: Quote from: voltsandjolts on March 18, 2022, 04:42:10 pmUh. Yeah sure. They do work. The question is, for how long.Even the "specialty" high-temp LEDs are rated up to something like 100°C. Rarely over that.High temperatures will just drastically reduce lifetime (and probably elicit early failures for a number of them.) It may or may not matter depending on your application, but thinking it has no consequence is deluded.Neon lamps are a safe bet, with the benefit of drawing less power than halogen lamps, producing less heat and having a longer lifetime.https://www.intl-lighttech.com/instrumentation-sensor-light-sources/neon-lampsGiven the low current, you can power them using a Cockcroft–Walton multiplier. Or whatever is convenient for your use case.

author: voltsandjolts
author_rank: Unknown
timestamp: April 06, 2022, 05:46:16 pm
content: Quote from: SiliconWizard on March 29, 2022, 05:40:53 pmThe answer is at least 6 months @150C for the random types I use, nothing fancy.The OP is looking for 110-120C operation which is a walk in the park, will last way longer.

author: voltsandjolts
author_rank: Unknown
timestamp: April 06, 2022, 05:59:05 pm
content: Quote from: DavidAlfa on March 29, 2022, 05:00:02 pmThe manufacturer ratings are conservative, many parts work far above their temperature specification although with reduced lifetime. e.g. some PIC MCUs rated for 85C work surprisingly well at 200C for a couple of months. You can buy MCUs rated for 200C but they are hundreds of dollars and are often overkill for some applications. Long-term high temperature testing is needed to find which parts can reliably meet lifetime and temperature requirements. The applications I target are battery powered and hence lifetime of battery (at 150-200C) limits the useful life of the system, hence lifetime requirements of semiconductors (these are one-time use products anyway).

author: Zero999
author_rank: Super Contributor
timestamp: April 06, 2022, 07:54:27 pm
content: A couple of transistors and a transformer can be used to generate 120V from 28V, but why bother? Use an incandescent lamp. High temperature silicone and fibreglass can be used for insulation.