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Hello Masters of Electronics,

I'm civil ingeneer, electronics are big unknown to me, but it wakes up my interest. I would like to control proportional pressure with electronic proportional pressure regulator. If I got right I need to control it with current from 0-1A at constant voltage of 18V. I would like to control it from Arduino.

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In last weeks I was looking for helping material on internet... and I found Youtube series from EEVBlog (https://www.youtube.com/watch?v=CIGjActDeoM ...Circuit is shown at time 20:00) about making own Power Supply Unit. I took out "Costant Current" part, bought 18V, 1A Adapter... Here is Shematic pdf to download LINK

First I would really apreciate if someone can take a look onto Shematic and check if it is fine.

Secund thing...I want to reduce Arduino output 0-5V to 0-1V. I tried to do it with putting resistor in series in ratio 4:1 (look at shematic) but I doesnt work, I get much lower reduction as expected. Whats wrong, how ca I achieve it.

Instead of 1Ohm at the end I put 5Ohm resistor at the end for now...I expected current from 0-1A, but I got just 0 - approx.0,6A. Why is this like that?

Any help, suggestion, comment is highly appreciated.

Regards, Damir

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  • \$\begingroup\$ First you need to fix your requirement: A supply can't dictate the current drawn while holding voltage constant. If you want to control the current, you will have to allow the voltage to vary too, though you may constrain that within some limits, where the mode switches and the current is no longer that desired. \$\endgroup\$ – Chris Stratton Jun 14 '15 at 16:37
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You began with the constant current power supply design that Dave shows in the linked video at 20:00. His design is good, as usual. (To save an op-amp, watch later at 28:45 in the video. Alternatively, the buffer and adder could be combined.) You put the solenoid at the input to the LT3080 which will allow its current to be controlled, and this current will be drawn from an adapter that can deliver 18V 1A max.

Whenever using an integrated circuit you should read its data sheet, in this case here http://pdf1.alldatasheet.com/datasheet-pdf/view/349922/LINER/LT3080.html . I think there will always be a current into the Vcontrol pin so unless you tolerate that as minimum current in the solenoid, feed that pin separately direct from the 18V supply.

You may have loaded the Arduino output with too low value resistors. To reduce the 0-5V average to 0-1V, replace the 10kohm resistor connected to the Arduino by 40kohm followed by 10kohm to ground.

If the buffer supplies 1V (check it) and so does the LT3080 to the 1 ohm resistor, the current is 1A as planned.

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