4 to 20 mA Current Loop Controller used DAC0832

Status
Not open for further replies.
O

otomatis

New Member
Hi all,

Does somebody have tried to build 4-20mA converter using IC DAC0832 (datasheet on page 20)...?

I have been build it but its not working. I was test the input data by SPST toggle switches to ground but the output always 18.9mA (single supply 12vdc 500ma) although switch has changed (0...255).
I could not find the 92PE37B transistor in my country so i changed to 2sc4408.

Could somebody help me, why is it not working...?
 
That's a floating circuit so do you have the switches going to the DAC common, not circuit ground?
 
Last edited:
otomatis said:
I have connected the switches to pins 3 and 10 of the DAC. Is it your mean..?
Click to expand...

hi,
I guess you know its a two wire system.??

You measure the 4 to 20mA in the low side of the "0"v [ 4-20ma] of the power supply to the project.??

Whats the voltage powering the circuit.?

EDIT:
added image
 

Attachments

  • AAesp01.gif
    23.9 KB · Views: 630
Last edited:
I put digital ampere meter instead of "ext sense resistor" to measure the 4 to 20mA. Supply is 12vdc 500ma for output 18.9mA. and
Supply is 16vdc 500ma for output 25.3mA.
 

Attachments

  • mysch.gif
    23.9 KB · Views: 379
Last edited:
otomatis said:
I put digital ampere meter instead of "ext sense resistor" to measure the 4 to 20mA. Supply is 12vdc 500ma for output 18.9mA. and
Supply is 16vdc 500ma for output 25.3mA.
Click to expand...

If it draws those 500mA supply currents when running they are far too high.!

How are the DAC parallel inputs connected and what are they referenced too, ie: which ground.?
 
I just follow the schematic in the datasheets on page 20. parallel Input connect to pins 3 and 10 (gnd) when logic is low (switch close/on) and floating when switch open(off).
 
otomatis said:
I just follow the schematic in the datasheets on page 20. parallel Input connect to pins 3 and 10 (gnd) when logic is low (switch close/on) and floating when switch open(off).
Click to expand...

hi,
I know how to set the status of the parallel pins, what I am asking is which grounding point are you connecting the 0V of the select switches.

If you are using an external ground are you using the opto isolators as specified on page #20.?

Also how are you switching the Control pins of the DAC.?
 
Last edited:
Hi Eric,

I make it low. CS(PIN1), WR1(PIN2), WR2(PIN18) and XFER(PIN17) are connected to ground of DAC (PIN3 & 10). I have replaced ic dac0832 with new one but the result still same ( output is 18.9mA).
 
Also how are you switching the Control pins of the DAC.?[/QUOTE]

ericgibbs said:
How are you switching the Control pins of the DAC.? Write, CS and Xfer.??
Click to expand...


Hi Eric,

I make it low. CS(PIN1), WR1(PIN2), WR2(PIN18) and XFER(PIN17) are connected to ground of DAC (PIN3 & 10). I have replaced ic dac0832 with new one but the result still same ( output is 18.9mA).
 
otomatis said:
Also how are you switching the Control pins of the DAC.?
Click to expand...

Hi,
You cannot just wire the control pins to fixed voltage levels, you must switch the control pins as described in the d/s in order to load/latch the data into the DAC input buffers.
 

Attachments

  • 000esp01.gif
    26.2 KB · Views: 186
Last edited:
I put digital ampere meter instead of "ext sense resistor" to measure the 4 to 20mA
Click to expand...
You are shorting the output with out a load resistor. Use a load resistor in series with your ampmeter. Andy
 
Status
Not open for further replies.

Similar threads

D
  • Question
Simple 4-20ma Current loop RF TX RX
Replies
9
Views
2K
rjenkinsgb
I need some advice on building a battery charger for my bank of 20 Li-ion 5000mAh 26650A
2
Replies
20
Views
2K
sheffieldyorky
  • Question
Tyre inflator modification. Currently powered by cigarette lighter, want to add mains power option.
Replies
14
Views
6K
ChrisP58
R
  • Question
Charging a Lifepo4 with a power supply and control current with a solid state relay controller by pwm. Good idee?
Replies
4
Views
2K
Rory1984
R
S
  • Question
Any one used STHS34PF80?
Replies
2
Views
1K
Sophia Zeng
S
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…