In one of my projects I need to generate different kind of 220V amplitude waveform signals in order to send commands to a heater using the pilot wire protocol. Here are the needed waveforms:

enter image description here

Is there a way to use a DAC and then amplify the output of the DAC to a 220V amplitude. If yes which circuit and components can I use.

Otherwise I am open to other price and size optimal circuits to get such waveforms.

Many thanks

  • 1
    \$\begingroup\$ You have not said a lot about the proposed load, or about the frequency range. Is 220V peak-to-peak or what? \$\endgroup\$ Nov 13, 2018 at 4:47
  • \$\begingroup\$ Hi @SpehroPefhany, yes 220V is peak to peak, and the purpose of proposing a DAC is being able to generate multiple frequencies, even extremely low frequencies (under 1 Hz). For a clearer insight it's for a heater pilot wire for which you can find the needed waveforms at: goo.gl/CnnD1k \$\endgroup\$ Nov 13, 2018 at 5:02
  • 3
    \$\begingroup\$ Those are all modifications of the line voltage. You can manage all of them by switching the line voltage through solid state relays and diodes. A DAC and amplifier would be the expensive (and hard) way to generate those signals. \$\endgroup\$
    – JRE
    Nov 13, 2018 at 6:14
  • 1
    \$\begingroup\$ I have a very hard time believing that a 230VAC appliance requires 220 volt peak-to-peak to control, it would be crazy. Your diagram only shows different easy modifications of the standard AC voltage (which is not peak-to-peak) \$\endgroup\$
    – pipe
    Nov 13, 2018 at 13:00
  • 1
    \$\begingroup\$ The signal here is intended to be one easily derived from the mains supply, but it is a distinct wire not actually used to power the heater (input impedance is supposed to be >= 100K): radiateur-electrique.org/fil-pilote-radiateur.php (google translate renders something relatively readable if necessary) \$\endgroup\$ Nov 13, 2018 at 15:49

2 Answers 2


A DAC and amplifier would be the expensive and complicated way to control the heater.

You have 230VAC at hand - you must, because that's what the heater operates on.

Use that 230VAC source, a few SSRs (solid state relays,) and a couple of diodes.

The control signal doesn't seem to drive the heating element directly. The commands seem to be just that: commands to a controller in the heater. That means you don't have to switch high power, and can use small SSRs and diodes to make the control signals.

Take the simple cases first:

  1. Confort

  2. Confort -1

  3. Confort -2

  4. Eco ou reduit

All four can be handled by one relay:

  1. Relay open

  2. Cycle relay 4 min 57 seconds off, 3 seconds on

  3. Cycle relay 4 min 53 seconds off, 7 seconds on

  4. Relay on

Each of the other two cases require a diode and relay each. Put a diode in series with each relay, each diode points in a different direction.

Now, you turn off the main relay, and turn on one of the two relays with a diode. Each sends a different command

  1. Use zero crossing SSRs. These switch when the AC voltage crosses zero volts.

  2. Use SSRs rated for use on 230VAC.

  3. Use diodes rated with a peak inverse voltage of more than 300V.

  4. Use diodes rated to handle more current than the command circuit requires.

Doing that, you can use three digital outputs from a microprocessor to send all commands.

Be very careful when working with 230VAC. There are many safety practices you should follow: look them up, learn them, apply them. Failure to do so can kill you.

There are many design practices to follow when designing and laying out circuits that use 230VAC. Look them up. Learn them. Follow them. Failure to do so might burn down your house or electrocute you or someone using the device.

  • \$\begingroup\$ Thanks for the answers, I guess I can use Triacs instead of relays, right ? \$\endgroup\$ Nov 15, 2018 at 1:17
  • \$\begingroup\$ SSRs isolate your low voltage microprocessor from the line voltage. If you can safely do it with triacs, then that's OK. \$\endgroup\$
    – JRE
    Nov 15, 2018 at 6:04
  • \$\begingroup\$ OptoTriacs may do the trick I guess \$\endgroup\$ Nov 15, 2018 at 7:27
  • \$\begingroup\$ An SSR is an optotriac with additional circuitry built in to provide safety and reliability when things go wrong. So, you could probably use bare optotriacs - if the additional risk is small enough that you can use the cheaper part. \$\endgroup\$
    – JRE
    Nov 15, 2018 at 9:49

A common-base transistor will do this. Drive the emitter from a current-output DAC. Tie the collector thru 100,000 ohm resistor to 220 volts DC. Peak current will be (at 10uA/volt) 2 milliAmps. Power power dissipation will be 1mA * 110 volts, or 0.11 watts. Be sure 0.11 watts is Safe Operating Area acceptable.

  • \$\begingroup\$ Perhaps, but application to existing appliances doesn't actually require arbitrary signals, but only those which can be derived simply via rectification and gating of the mains supply waveform. \$\endgroup\$ Nov 13, 2018 at 15:52

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