Power supply problems

  • #1
I've got an old laptop charger 19v 3A for my solenoid.
I used a multimeter to check the charger without and with load. I used a solenoid of insulated 22gauge of approx 150 turns as the load. On my first try without any load, it gave 20v DC on the multimeter.
When I connected the load and connected the multimeter ,it gave values on AC part fluctuating back and forth from 0-1.5v . Can anyone help me out in this? Is there anyway to get DC out of it while on load ?
 

Answers and Replies

  • #2
berkeman
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I've got an old laptop charger 19v 3A for my solenoid.
I used a multimeter to check the charger without and with load. I used a solenoid of insulated 22gauge of approx 150 turns as the load. On my first try without any load, it gave 20v DC on the multimeter.
When I connected the load and connected the multimeter ,it gave values on AC part fluctuating back and forth from 0-1.5v . Can anyone help me out in this? Is there anyway to get DC out of it while on load ?
You are shorting out its output, so it is in current limit until you remove the short.

You need to put a load of about 19V/3A = 6.3 Ohms on it to keep it out of current limit.
 
  • #3
You are shorting out its output, so it is in current limit until you remove the short.

You need to put a load of about 19V/3A = 6.3 Ohms on it to keep it out of current limit.
I tried 6ohms ( I don't remember correctly,but it's close to 6ohms) and the solenoid literally ceased to function :(
 
  • #4
berkeman
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I tried 6ohms ( I don't remember correctly,but it's close to 6ohms) and the solenoid literally ceased to function :(
What wattage resistor did you use? I^2 * R = 54W, so you would have needed a pretty big power resistor...
 
  • #5
jim hardy
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#22 is 16 milliohms per foot.

How many feet of #22 would it take to make six ohms ?
On your solenoid's diameter, how many turns would that be ?

Do you understand the relation between amp-turns and magnetic field strength ?
You might look that up . Train your search engine - it wants to please .
 
  • #6
davenn
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I tried 6ohms ( I don't remember correctly,but it's close to 6ohms) and the solenoid literally ceased to function :(

not surprised .... your LOAD, the coil, needs to be around 6 Ohms ... not a 6Ohm resistor in series with it :smile:


Dave
 

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