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Constant current issue

CKaiL

Oct 10, 2014
12
Joined
Oct 10, 2014
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I have built a circuit. It is working when I tested it using a 9V battery and using a arduino board to generate a constant 5V supply. However , when I connect it to the power supply , the indicator from the power supply change from constant voltage to constant current.
It is working and everything work according to the way i want it to go when it is between 1.5~1.7A . What do you think is happening? Is there a short circuit or?

One thing i notice is that when I try to increase the constant current more and eventually the indicator changes to constant current to constant voltage . The circuit is not working although the LED in my circuit light up and i cant control it.
 
Last edited:

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
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25,510
If the indicator on your power supply changes from constant voltage to constant current, this is an indication that your load is trying to draw more current than you have set the current limit to. In response to this, it reduces the voltage to keep the current at (or potentially below) the set current limit.

Please try to answer all of these questions:
  1. Does your power supply indicate the current being drawn? If not, can you measure it?
  2. What voltage is your power supply set to?
  3. Are you certain the polarity is correct?
In addition to this, a circuit diagram and a photo may be of assistance.
 

CKaiL

Oct 10, 2014
12
Joined
Oct 10, 2014
Messages
12
If the indicator on your power supply changes from constant voltage to constant current, this is an indication that your load is trying to draw more current than you have set the current limit to. In response to this, it reduces the voltage to keep the current at (or potentially below) the set current limit.

Please try to answer all of these questions:
  1. Does your power supply indicate the current being drawn? If not, can you measure it?
  2. What voltage is your power supply set to?
  3. Are you certain the polarity is correct?
In addition to this, a circuit diagram and a photo may be of assistance.

1. I am not really sure about this
2. Before I output , I set the power supply to 9V with 0.5A. However , when I connect it to my circuit , the voltage drop to about 5.4 and current is about 0.16A
3. I am certain i have connected it correctly. eg Ground to ground

I have indicated wrongly in my post above it should be 0.15A to 0.17A and not 1.5 to 1.7A
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
OK, that's useful information. Now, arising from that,
  1. Do you have a multimeter?
  2. if so, do you know how to measure current?
  3. if so, can you measure the current draw from the power supply when this device is connected?
  4. When powered from a 9V battery, what was the voltage as measured across the battery with this device connected?
  5. When powered from a 9V battery did the 9V battery get warm?
  6. Can you provide a schematic so we know what the circuit is?
 
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