Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

[SOLVED] Power supply measurment

Status
Not open for further replies.
C

cipi-cips

Member level 4
Joined
Jun 30, 2008
Messages
76
Helped
2
Reputation
4
Reaction score
1
Trophy points
1,288
Activity points
1,867
Hello,

If someone can help me with testing power supply,

I have one power supply that has output of 12V and the maximum current is 400mA but voltage drops to cca 6.3V. These are the information I got from power supply manufacturer. I have made some test but didnt get same results. This is how I made test:

sli.png

I was able to to get 200mA but only when I very very very slowly moved potentiometer. After that nothing.

Is there any alternatives for measuring ?

Thx
 

Your best bet is a 30 Ohm 5W resistor as a load. That will pass 400mA when 12V is applied. The trouble with your variable load is the setting will be fairly critical and unless you have the BD234 on a large heat sink, it will drift as it warms up.

Brian.
 

You need some simple feedback to help you maintain the required current load. The idea below can be used or modified to your requirements. As mentioned, you need a decent heat sink for the main transistor.
 

Attachments

  • e_load.png
    e_load.png
    8.4 KB · Views: 94

THx for reply,

This is the exact situation I am facing, while moving potentiometer from one end to another I start to see raise in the current from 0mA - 10mA and voltage is dropping from 12V to 11V ect. after I reach cca 20mA (voltage is 9.1) if I move very very very very slowly potentiometer current keeps to raise but it last like second or two then back to 10mA and voltage drop is belove 5V.

Thanks for help
 

Hi,

Sounds like there is a polyfuse or any other current limiting circuit in the power supply.

Klaus
 

Do you have any specifications you can post for this supply??
 

I presume your power supply is not working well. I guess it is expected to provide regulated voltage output of 12V with current upto 400 mA. Voltage drop of more than 0.1 or 0.2V is generally not acceptable.
 

Thx for all your reply,

Problem was in power supply it was damaged.

Thanks
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top