I need circuit (or idea) how to drive proportional valve -10...0...+10V, using xmega D/A converter (0...3.3 V)
A basic op-amp circuit, powered from +/-15v rails will do it.
You need to scale the 3.3v swing up to 20v, so a gain of 6, and then offset it by -10v. In reality, you do the offset first to give you -1.66 - +1.66v and then apply the gain.
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How many ma to drive the valve? Get a hi output opamp.
Imagecraft compiler user
Valve spec says current is 10 mA.
I may need 4 D/A output, 2 for 0...+10 V and 2 for -10...+10V, so I will try DAC which can generate directly -10...+10 V (AD5722 or similar). Other 2 outputs (0...10V) xmega D/A + opamp.
I presume the valve slew rate is pretty slow in which case PWM -> LPF -> add -ve offset -> amplify -> buffer.
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