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PID question

post #1 of 5
Thread Starter 

I am in the process of building an electric smoker and know nothing about PID controllers. I've done a lot of reading & searching but I don't think I understand everything I know about PID's. Curious if this one is usable to run a 3500w 240v broiler element that I have on hand and I'm planning on using, might be over kill but it's what I have. The PID in question is a mypin brand, don't know if that's good, bad, or otherwise but it fits my budget and has decent online reviews. Sorry for the length of the post but I didn't know what might be relevant.  Thanks for any input. Jack

 

Here are the specs.

 

Product Introduction:

This is a set of temperature controller TA7-SNR,PT100 and solid state relay-SSR-25DA. The dual line display universal digital programmable temperature controller supports many types of thermocouple sensor. It can also worked as simple digital adjustor.

Feature:

  • Compact design, great form-factor to be included/build-in to your product.
  • One key operation, Auto-tuning PID control.Easy operation,Reliable performance
  • Input: TC(K、J、S、E)/ RTD(Pt100、CU50)universal input, (24V/30mA supply available for standard transmitter)
  • P, I, d, controlling period, digital filter coefficient, and more… (for control theory experts only)
  • SSR control ready to connect external Solid State Relay to handle High current.

Specification:

  • TDisplay: Dual display for Fahrenheit(F) and Celsius(C)
  • Range: -1999 to 9999 (depends on the input signal)
  • Input: Thermo Resistor: PT100, Cu50
  • Thermocouple: J,S,K,E,
  • Main output: SSR, open circuit: 4V, Closed Circuit: 24V 40mA DC
  • Auto-tuning PID cooling/heating control( can choose normal alarm output by software)
  • Alarm Output: 1 RELAY: capacity 250V/3A AC, 30V/3A DC
  • 7 different Dual Output modes with: high / low / high deviation / low deviation/ interval / out of interval /breakage alarm
  • Accuracy: 0.2%
  • Width switch power: 90-260V AC/DC
  • Dimension: (72WX72HX72Lmm)

Accessory 1: Solid State Relay:

  • Model no.: SSR 25DA
  • Load Voltage: AC 24-380V
  • Load Current: 25A
  • Input Voltage: DC 3-32V

PT100:

  • Measure range: -20~420℃
  • Element:Pt100(Platinumi)
  • Material: stainless steel 304
  • length: 6 feet(2m)

Package Content:

  • 1x temperature controller, model no.: TA7-SNR
  • 1x solid state relay,model no.: SSR-25DA
  • 1x PT100
post #2 of 5
looks like you should be good to go... the power for the element doesn't go through the controller.. it goes through the SSR (which is rated up to 380V) ... the controller just controls the SSR with a low voltage (24V) signal....
post #3 of 5
The SSR should be good for your application.

3500 Watts divided by 240 Volts gives an operating current of about 14.6 Amps for your heating element. The SSR is rated for 25 Amps, so you've got plenty of capacity there.

But be sure you are adequately heat-sinking and ventilating the SSR to keep it cool enough. (Assuming it does not have a built-on heatsink).

SSRs always have some voltage drop across their SCRs or TRIACs. And those semiconductors must have their junctions kept from overheating. Remember that most semiconductors' lives are cut in half for each ten degrees C increase in die temperature. So cooler is always better for electronics.

Just a ballpark guess would be that your SSR will be dissipating about 30 Watts when your heater is switched on. So you will need a heatsink (and adequate airflow to it) to give a low enough thermal resistance that this will keep the SSR's die at a safe temperature.

The SSR manufacturer should be able to give you the thermal resistances for the insides of the SSR as well as thermal derating curves for the device.

And heatsink manufacturers give the thermal resistance curves for their heatsinks mounted in various orientations in free air or with forced airflow, and for various ambient temperatures and air densities, etc.

And remember to use good thermal joint compound when mounting the SSR to the heatsink to reduce the thermal resistance of that junction.

Also, be safe with your wiring, connections, and assembly of it all. Use high temperature connectors and wire for the connections to the heating element. Use proper wire sizes and connector torques, etc.

Done right, a setup like this will be safe and long-lasting. But there are a lot of considerations. If in doubt, ask more or consult an expert.

Tabbed in.
post #4 of 5
Thread Starter 

Thanks for the tips. I have it all hooked up and running with thermal paste and heat sink. It was pretty straight forward and is running pretty sweet. Seems kinda funny to be asking these questions since I work with 480v 3ph electricity every day. We even have some PID controllers on equipment but I have never "built" a control panel before. Again thinks for the help.

post #5 of 5

Sounds like you got it figured out.  The key is to remember the PID is just generating the control signal for the SSR.  The PID is not really the "switch" carrying the load, the SSR is performing that function.

 

If you don't already have the TA4 programming manual, there is one posted in this thread.

 

http://www.smokingmeatforums.com/t/148997/mypin-ta4-pid-manual-programming-instructions-and-general-pid-ssr-info-by-request

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