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TEC Chill Box Chamber Build log - Page 8

post #71 of 1662
Thread Starter 
http://www.ebay.com/itm/DIY-2015-Advanced-Starter-Learning-Kit-for-Arduino-Sensor-Module-Board-W-Box-/161805814290?hash=item25ac60ca12:g:wGwAAOSw3ydV3WNd

so you guys are building this stuff?

http://www.ebay.com/itm/DC-12V-Digital-Temperature-Controller-Thermostat-F-Peltier-WH7016K-/391304879091
http://www.ebay.com/itm/Digital-Humidity-Control-Controller-110V-WH8040-Range-1-99-RH-HM-40-Peltier-/390706219009

these might make it a little easier to do anyway, thanks for the info, I was wondering how it was done.
post #72 of 1662
Thread Starter 
http://www.amazon.com/Relay-Harness-Bosch-Style-40AMP-HRNS/dp/B005HFYE1O/ref=pd_bxgy_263_img_3?ie=UTF8&refRID=0AN0EMPR4HWG9JPZ7V19
LiamG6
for that amp issue your having

http://imgur.com/SVkxlRF



put the arduino where the switch is.
post #73 of 1662
you want to avoid using relays with TEC's, they are more suited to being controlled with variable DC voltage or PWM, PWM is how my controller works, but there is a 20amp maximum with some sort of safety circuitry on the control board. I was simply going to wire in a 20a schottky diode from the +v in to the +v out so that the startup current would divert around the controller, as the TEC chills down a bit it pulls less amps and then will be below 20a, so the current will flow to the controller rather than through the schottky diode. I may be confused about the function of the diode though, as it may only shunt an over voltage, rather than over current, I'm sure someone will pipe in and point me in the right direction before I blow anything up tongue.gif EDIT: actually I think I'm completely wrong and am thinking of some other device that will divert based on over current rather than voltage, possibly that relay you linked ;-)

Mindchill, foxrena and Ultrasonic have all made their own controllers, there may be others but the only ones that were for sale were from mindchill which is what puck is using, they are no longer available, foxrena and ultra only made controllers for themselves, both based on arduinos. mindchill has a fully custom setup. lmlarklar recently made one for himself on here that was a variable dc one, but it was complicated.

Basically you use an arduino to control a mosfet, the arduino outputs a pwm signal, you measure the ambient temp and humidity level and you can use a mosfet to control the TEC to stay above dew point from that. it requires a bit of circuit building and a bit of coding, mostly just find existing code that others have made and make it work for what you need to do.
Edited by LiamG6 - 1/11/16 at 5:51am
post #74 of 1662
Thread Starter 
in my test build, my TEC was wired directly to my power supply, and every time I would turn it on the power supply, the TEC would make a snapping sound, this sound is not good for the TEC, or the power supply, but with the relay in the circuit, it provides enough of a delay in how the load is given to the TEC, that it does not make the snapping sound anymore.



this is how I have setup my TEC's
PS to relay controlled by a switch then to the TEC.
liamG6
you want to avoid using relays with TEC's, they are more suited to being controlled with variable DC voltage or PWM, PWM is how my controller works, but there is a 20amp maximum with some sort of safety circuitry on the control board

I don't understand why you would say not to use these relays, stuff like this is what they where made for, I plan on placing a arduino with does output in PWM, in the same place as the switch later, as a upgrade to the system to make it more of a automatic process.
post #75 of 1662
Thread Starter 
in my test build, my TEC was wired directly to my power supply, and every time I would turn on the power supply, the TEC would make a snapping sound, this sound is not good for the TEC, or the power supply, but with the relay in the circuit, it provides enough of a delay in how the load is given to the TEC, that it does not make the snapping sound anymore.


Edited by toolmaker03 - 1/11/16 at 6:17am
post #76 of 1662
if controlling TEC's via a relay it subjects them to thermal cycling which can damage them, ie on for a few seconds and then off for a few seconds, or on for a few minutes and then off for a few minutes, this can damage the TEC, PWM on the other hand is great as you can run it at high frequency switching speeds which don't subject the TEC's to thermal cycling. If you are just usign the relay to turn it ona nd then leaving it on that is fine, but if you are using a relay to maintain a set temp that is achieved by repeatedly turning the TEC on and off it will damage it. PWm is better, variable DC is better still. Relays switch far too slowly to be used with PWM to control them, you need to use mosfets with PWM.

My controller is rated for 20a, at 0*c dT the 669w TEC I'm using will pull 25amps at 12v, so at startup the TEC needs 25a, but my controller has some safety circuitry that won't allow that, so it just doesn't switch on, once the TEC drops to about a 30*c dT it pulls about 18amps, which is fine for my controller. So I need some way for it to automatically divert the power straight to the TEC when it pulls more than 20a and then switch back to the controller when it settles in to normal operation at 20-30*c dT. I'm not too fussed as it seem to be fine for me at constant 12v for now, keeping my CPU nice and chilly tongue.gif, eventually I may try to solve it, or even modify my controller so it can handle more amps, it only has 1 mosfet, would need to use more mosfets and change whatever safety circuitry is on it to allow more current.
post #77 of 1662
Thread Starter 
yes right now it is a straight switch and the relay does not shut off from heat as it is a 40A relay with about a 25A load during startup but it is a 20.9A normal.

thanks for that I thought I was doing something wrong for a sec.

so I will not have the arduino output to the relay in a PWM single, but a on/off or high/low signal, it will be based on water temps, with a long hysteresis so that it is not going on and off all the time.
the only time the arduino should turn a TEC on, is if I am playing a game, and it should turn the TEC off, after I shut the game down.

too much to explain, but yea this is what I am doing as of right now, the relay is controlled by a manual switch that I turn on and off.
http://www.amazon.com/HOT-SYSTEM-ON-OFF-Rocker-Motorcycle/dp/B00RZ4YTCO/ref=pd_sim_422_77?ie=UTF8&dpID=41lxh3PWcVL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=0K8CVQ4CDHX7CG8BXMWN

http://imgur.com/y9HfiAK
post #78 of 1662
Thread Starter 
on a side note these relays get hot, at 20.9A after about 20min you cant touch them, so if one where installing the relay into a three switch electrical box, how would one cool these things?
I have seen some heat sinks that are made for these types of relays, and I could get a few of them, to attach to the back of the relay, and two small 30mm 12V fans to install on the top and bottom of the box, would that be enough?
Edited by toolmaker03 - 1/11/16 at 7:26am
post #79 of 1662
Thread Starter 
http://imgur.com/a/adbbn

ok so I have three of these cheap CPU air coolers, that I have had in a box for years.
they might be a little much, but I think that they will keep the relays cool enough, I will drill and tap a hole in the cold plate of the CPU cooler for mounting the relay to them, and then I will build a little plastic box to go around the relay, and attach to the bottom of the CPU cooler where the motherboard mounting used to be.

not what I was wanting to do, but I have this stuff, so I might as well make use of it.
post #80 of 1662
If these relay get hot within rated current, that indicate high resistance on contact (cheap?), you can try to measure between pin 30 and 87 when relay is energized, an ideal contact should read 0v (not going to happen) higher the voltage drop, hotter it gets. You can try to use 2 relay wire in parallel to share the load current see if that helps. Also are you sure those snapping noise are from TEC and not from the power supply itself?
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