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

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Discussion Overview

The discussion revolves around the use of a 19V 3A laptop charger to power a solenoid. Participants explore issues related to voltage readings under load, the appropriate load resistance, and the functionality of the solenoid when connected to the charger.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant reports measuring 20V DC from the charger without load and fluctuating AC values (0-1.5V) when a solenoid is connected.
  • Another participant suggests that the charger is in current limit due to a short circuit and recommends using a load of approximately 6.3 Ohms to avoid this issue.
  • A participant mentions trying a 6 Ohm load but states that the solenoid ceased to function.
  • There is a query about the wattage of the resistor used, with a calculation indicating a need for a high-power resistor (54W) for a 6 Ohm load.
  • One participant discusses the resistance of the wire used in the solenoid and questions the relationship between amp-turns and magnetic field strength.
  • Another participant clarifies that the load should be the coil itself, not a resistor in series with it.

Areas of Agreement / Disagreement

Participants express differing views on the appropriate load for the charger and the functionality of the solenoid under those conditions. The discussion remains unresolved regarding the best approach to achieve the desired operation of the solenoid.

Contextual Notes

There are uncertainties regarding the exact resistance needed for the solenoid and the implications of using a resistor versus the solenoid itself as the load. Participants also discuss the power requirements for resistors without reaching a consensus.

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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