Power supply problems

1. Jul 10, 2017

Anugrah_kora

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 ?

2. Jul 10, 2017

Staff: Mentor

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. Jul 10, 2017

Anugrah_kora

I tried 6ohms ( I don't remember correctly,but it's close to 6ohms) and the solenoid literally ceased to function :(

4. Jul 10, 2017

Staff: Mentor

What wattage resistor did you use? I^2 * R = 54W, so you would have needed a pretty big power resistor...

5. Jul 10, 2017

jim hardy

#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. Jul 10, 2017

davenn

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

Dave