| Electronics > Beginners |
| Can a variable thermal shut off circuit be build? |
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| digsys:
--- Quote from: FriedMule --- It is always dagerus to say that the price dos not matter, but I'd rather that it WORKS!! then save a few dollars ... --- End quote --- NO ONE suggested that the "cheap(er) price of ~$100 reflected poor quality" !! Crydom is one of the very best solid-state manufacturers out there. I was replying to ledtesters comment = "I looked up what a 75A solid state relay costs at Mouser and was shocked". I don't know what price ledtester saw or what part he was actually looking at, or what he thought was "expensive". ~$100 is an extremely good price for that type of device ! --- Quote from: FriedMule --- ... What about optorelays, do they not have to handle great amount of current and voltage? --- End quote --- That is an "opto-relay". 100V at 75A+ |
| ledtester:
--- Quote from: FriedMule on August 01, 2019, 11:05:26 pm ---Yes 75A is an insane amount og current, but nice to have, because, hmm, just nice to have. :-) The 75A is a 10V unit and I do newer think I'll use that many amps, but why not build so it can be used? --- End quote --- There is something to be said for using a power supply that is sized for your application. You want some headroom, but using a 75A power supply when you only need a couple of amps is foolhardy. Even if the supply has current limiting, 750W is a lot of power, and it's a good idea, especially for beginners, to limit the worst possible outcome to something that's not going to ruin your day. At the very least employ fuses that are appropriate to your application. --- Quote ---... I imagine some sort of turn button that when turned, changes the max temperature on a display and if the real temperature on the probe is going above, then off! ... --- End quote --- These things are called "temperature controllers" (and in the consumer world "thermostats") and there are a ton of ready-made bare modules available with a "dial" and display. The difficulty is finding something that will work at the temperatures you want and uses a sensor that is compatible with your application. Thermistors and thermocouples are generally used to measure the temperature of a heatsink / battery / electronic component. You might also find some pre-made modules by searching for "fan controller". I just recently bought one of these: https://www.ebay.com/itm/12V-PWM-Fan-Temperature-Speed-Controller-Module-High-Temp-Alarm-5V-Buzzer-PC-CPU/263605466941?hash=item3d601c373d:m:md_Xw7-TdWpozYJ83KekdBw Haven't had a chance to test it out though. |
| CatalinaWOW:
Your supplies should have a remote turn off option which will do the job nicely. I know you have said you don't want to turn off the supplies so you can maintain a long on time on your test circuit for "stability", but when you change the load current by that amount all stability is out the window anyway. Those stability issues arise because of thermal effects primarily and when you dump the load you change the thermal environment completely. If you decide to stick with your plan as others have said temperature controllers are widely available. https://www.omega.com/en-us/search/?text=temperature+controller The ones in the link are pricey, but quality is assured. I am sure you can find Chineseum ones far cheaper. Then the only trick is to use the relatively low power relay (only a few hundred watts) in these things to turn off the high power contacter you need to find. |
| CatalinaWOW:
Here is a link to a far cheaper module https://www.amazon.com/Inkbird-Temperature-Controller-Thermostat-Itc-100VL/dp/B0148FS5FO/ref=asc_df_B0148FS5FO/?tag=hyprod-20&linkCode=df0&hvadid=167124686369&hvpos=1o3&hvnetw=g&hvrand=8827568315575995131&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033112&hvtargid=pla-304949473590&psc=1 |
| FriedMule:
Thanks a lot, you are all fantastic! About 75A being to much if I maybe only need a few amp. Yes that is perfectly correct and I do have some 30V 5A and other that I can use for the normal everyday use. What I am looking for, is the possibility to turn off the PSU no matter what PSU I choose to use, if it is my 30v-5A, 10V-75A, or my 100V-10A. I'll take a look on the thermostats! :-) |
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