Power Supply Problem: 19V 3A Laptop Charger + Solenoid

AI Thread Summary
The discussion centers on using a 19V 3A laptop charger to power a solenoid, where the user observed a voltage drop and fluctuating AC readings when a load was connected. It was noted that the charger may be going into current limit due to an improper load, suggesting a need for a load of approximately 6.3 Ohms to maintain proper function. Attempts to use a 6 Ohm resistor resulted in the solenoid ceasing to function, indicating that the load should be the solenoid itself rather than a resistor in series. Participants emphasized understanding the relationship between amp-turns and magnetic field strength for effective solenoid operation. Proper load matching is crucial for the charger to deliver stable DC output while under load.
Anugrah_kora
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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 ?
 
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Anugrah_kora said:
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.
 
berkeman said:
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 :(
 
Anugrah_kora said:
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...
 
#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 .
 
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Anugrah_kora said:
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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