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In my current project, I am controlling Peltier Element Temperature which is current controlled load using Arduino. I am controlling Temperature of Peltier by applying PWM to H-bridge.

In addition to this, I have to change the polarity of Peltier Element. For this functionality, I am using two Electro Mechanical Relay. Once Relay starts switching it makes the controller Reset.

What could be the possible reason for this error? And How could I solve it?

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    \$\begingroup\$ Please post a circuit diagram. Please. \$\endgroup\$ – MrGerber Mar 21 '18 at 7:53
  • \$\begingroup\$ Do you use same voltage source for Arduino and the relays ? \$\endgroup\$ – Long Pham Mar 21 '18 at 7:55
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    \$\begingroup\$ Why use an H Bridge and then change polarity with a relay? Surely you could do that with the H bridge? \$\endgroup\$ – Colin Mar 21 '18 at 9:05
  • \$\begingroup\$ Also, PWM is not a good way to drive a peltier, electronics.stackexchange.com/questions/28634/… see Olin's answer here, and electronics.stackexchange.com/questions/118536/… here \$\endgroup\$ – Colin Mar 21 '18 at 9:06
  • \$\begingroup\$ Arduino being reset is "not good thing", it's probably because of inbuilt protection. Nothing more can be said without circuit diagram and knowing what exactly you're trying to do. \$\endgroup\$ – Deep Mar 21 '18 at 14:20
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if the maximum output current of the voltage regulator feeding the circuit is exceeded its output voltage drops causing a drop in the supply voltage of the chip in the arduino, and the chip resets if its supply voltage is under the minimum recommanded value giving in the datasheet.

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Probably when the relay coil releases, there is a big voltage (flyback) spike from the coil. You need a diode straight across the relay coil pins.

Alternatively there isn't enough power to energise the coils, and VCC is falling.

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    \$\begingroup\$ I might add that if he's using the Arduino to power the coil then that's also bad ? Consider using a transistor as a switch in series with the coil \$\endgroup\$ – Simeon R Mar 21 '18 at 8:17
  • \$\begingroup\$ In addition to the inductive kick, if there's any arcing across the relay contact when it opens, that could be generating transients that couple into the surrounding wiring, causing the processor to reset. \$\endgroup\$ – AlmostDone Mar 21 '18 at 15:57
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In my current project, I am controlling Peltier Element Temperature which is current controlled load using Arduino. I am controlling Temperature of Peltier by applying PWM to H-bridge.

If you use a H-bridge then you don't need relays to control current direction (polarity) because by driving the H-bridge appropriately you can get full supply reversal: -

enter image description here

Pictures from here.

If Q2 and Q3 turns off and Q1 and Q4 turn on you get current reversal: -

enter image description here

Once Relay starts switching it makes the controller Reset. What could be the possible reason for this error? And How could I solve it?

There could be several reasons: -

  • Bad circuit layout
  • Bad design
  • Power supply not sufficient to drive all loads
  • Flyback diodes required
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