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Topic: Driving a 0-10vDC signal control valve (Read 6436 times) previous topic - next topic

dhenry

You can create gain by inserting a resistor between the two 100k resistors and the output.

dc42

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dhenry

Quote
See attached.


It looks great, except that it wouldn't work.

StuntMonkeh


You can create gain by inserting a resistor between the two 100k resistors and the output.


So if I put a 100k resistor in where you said that would give me a gain of 2.

What does the 100k resistor thats currently located between the output and ground?

I know the circuit I found does not allow for any conditioning of the PWM.  I assume I will need some sort of low pass filter on the op-amp input.

zoomkat

Well, you could go to radio shack and get a rectifier to rectify the 24vac into a dc current, use some fat capacitors to smooth the DC ripple, and use a voltage regulating chip (7805, 7812, etc and some small diodes) or a pot to get the output voltage down to ~10v for the base signal. Crude, but might work.
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dc42


I know the circuit I found does not allow for any conditioning of the PWM.  I assume I will need some sort of low pass filter on the op-amp input.


The schematic I posted includes the low pass filter.
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slawa92

Hi, Im having troubles with 24V AC valve as well, I figured out the way to get 10V DC signal, but the problem is that when I connect the valve (-) to arduino GND (the walve is powered by 24V AC) the current of the 24V AC transformer hits the skies, any suggestions ?

dave-in-nj

#22
Aug 31, 2016, 01:29 pm Last Edit: Aug 31, 2016, 01:34 pm by dave-in-nj
Hi, Im having troubles with 24V AC valve as well, I figured out the way to get 10V DC signal, but the problem is that when I connect the valve (-) to arduino GND (the walve is powered by 24V AC) the current of the 24V AC transformer hits the skies, any suggestions ?
the 24VAC cannot be grounded anywhere else
your Arduino has to get power from the 24VAC and that too, cannot be grounded anywhere else,  make sure you do not connect the USB at any point while in circuit.

[ EDIT : or tie one leg of the 24VAC to ground as it is floating from the transformer secondary.  As it is, it could be anywhere between ground and your mains voltage. ]


there are voltage rectifiers that  can take the 34 volts DC and convert to your 5V to drive your unit.  a simple LM2596 switching voltage regulator will not get hot from the larger voltage drop.

you might be able to get an linear opto to allow you to use a common DC circuit without having to tie into the AC side.

Europe HVAC controls are 24VAC 3 wire with DC controls as you mention.  Belimo has quite a few offerings for actuators as you describe.



Wawa

#23
Aug 31, 2016, 01:42 pm Last Edit: Aug 31, 2016, 01:49 pm by Wawa
Did you measure the 0-10volt signal input with a DMM.
Could be that 10volt is already on the input/ground of the device when nothing is connected to it.

0-10volt has been covered before.
https://forum.arduino.cc/index.php?topic=340922.0
Leo..

dave-in-nj

Did you measure the 0-10volt signal input with a DMM.
Could be that 10volt is already on the input/ground of the device when nothing is connected to it.

0-10volt has been covered before.
https://forum.arduino.cc/index.php?topic=340922.0
Leo..
what complicates his project is the floating AC. 
he either needs to ground one leg of the secondary. it should be marked + and - even though it is AC.
or allow the ENTIRE control system to float. 

Much of HVAC lives in 24VAC. being low voltage it does not have to be in conduit in commercial facilities like anything over about 48 volts does.

most of the european manufacturers that sell in to the US have sheets on how to work with 24VAC and control circuits.

http://www.kmccontrols.com/images/agiods_files/downloads/AN0604D-RevB.pdf



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