Adjustable DC bench supply question

[caphair]

It’s an Arksen 303D

Should you be able to adjust current limit and have it display the amount when voltage is set to 0v?

On mine the only read outs it shows is when adjusting voltage. Current stays at 0 until you apply a load then it just shows current draw

Is it faulty or this normal operation?

[mariushm]

Re: Adjustable DC bench supply question

I believe you have to short the output to see the current limit when you set it.
The display only shows the current voltage and current, not the current limit you adjust.

This is kinda typical of these cheap linear power supplies.

[budm]

Re: Adjustable DC bench supply question

No current flow = No current display, so you have to short the output to set the current limit but some cheap power supply will not allow you to do that, you'll need to read the instruction of the unit.

[caphair]

Re: Adjustable DC bench supply question

Thanks guys. Shorting the output worked. I saw a video of someone using a similar psu and they didn’t show or inform that’s what they did to show a current display when adjusting so made me curious.

Is there a way to adjust the voltage output of these? Mine displays for example 4v but an external meter reads it as 3.7v

[sam_sam_sam]

Re: Adjustable DC bench supply question

It depends on whether or not it has dedicated meter IC chip or something else

Look near the display LEDs and find the chip that display hook up to or the IC chip that is near that one you will know when found the right chip if on the data sheet for that chip 3.5 or 4.5 meter

Some thing like a ICL7107 or ICL7106 is more than likely in it if it has that chip it yes you can adj
it but be careful doing that because in these power supply there two or more of these adjustable pots

There is one pot that adjusts the high end voltage value this one is not a good idea to mess with unless you understand what that adjustment does because it also changes low end voltage also and it may not go to Zero volts when pot in front of the power supply in turn alway to left

There is a pot that adjustment pot for the current as well like voltage one you need careful not to play with this one either

One note

I done this before when I had fix one my adjustable power supply that the voltage protection diodes shorted out on the output terminals ( Do not ask how I managed to short out the diodes ——> I was doing something I knew better than to do this with it )

After I fix it and long before this it would not go up to 24 volts like should ( it would only go to about 22 volts) this how I found out what those adj pots did ( if you go to far with the adjustment at least with my power supply it put it protection mode and would not do anything until I unplugged it from the wall )

one side note

I was able to adjust the output voltage to a little over 26 volts with out affecting to zero volts reading with the two adjustment pots ( in the front of the power supply) turn alway turn to left this is very important to make sure this still works right

Also the voltage and current LEDs did not work right because the LEDs were going bad

After fixing this power supply it is back working like it used to

I hope this helps

[sam_sam_sam]

Re: Adjustable DC bench supply question

Thanks guys. Shorting the output worked. I saw a video of someone using a similar psu and they didn't show or inform that's what they did to show a current display when adjusting so made me curious.

Is there a way to adjust the voltage output of these? Mine displays for example 4v but an external meter reads it as 3.7v

If were me I would do nothing with 0.3 is not enough off to mess with it I explain that in the post above

[redwire]

Re: Adjustable DC bench supply question

The digital panel meters in these things have a CAL trim pot, so I would fix it.
0.3V off is a bit much working with 3.3 or 5V devices.

[sam_sam_sam]

Re: Adjustable DC bench supply question

The digital panel meters in these things have a CAL trim pot, so I would fix it.
0.3V off is a bit much working with 3.3 or 5V devices.

I agree with you on that point

(5 volt device can be a little off without to much of problem most of the time)( I do not know to much about weather or not 3.3 volt devices how much they can tolerate being over to comment on this)


I was just pointing out that you need to make sure you have the right trim pot that you are adjusting or other wise you can have your adjustable power supply in worst shape than you started with

I agree with you about the point that your voltage meter on your adjustable power supply should be correct when doing this

If you are charging lipo-batteries you need make sure that you have the correct setting for the current and the voltage as well if you charge them with OUT a protection board this is a must if charge batteries in general

I do from time to time charge batteries that require a protection board with out the protection board if I am having problems charging them but I am very careful doing this and when I do this I do not have the current set more than 500 millimeters at the most

[Longbow]

Re: Adjustable DC bench supply question

I'm not getting the point of this discussion. It seems like the OP does NOT have a supply with a current limit, but just a current readout. If a supply is actually designed with a limit function, it can be of 2 kinds. The first is a crowbar that shuts down the output when the current limit is reached. The fancier design is when the supply outputs a constant voltage until the current limit is reached. At that time, it switches into constant current mode, reducing the output voltage accordingly to keep the current steady at the limit point. You have to know what you need to do the job. CV/CC supplies are the way to go for a daily use supply. There are excellent deals on older HP supplies if you don't mind repairing them first.

[eccerr0r]

Re: Adjustable DC bench supply question

The "older" HP supplies demonstrate the need to short out the output in order to set the current limit. "newer" computer controlled supplies could double-purpose the display to set the current limit without needing to short the output to set the current limit.

I would imagine non-computer controlled supplies regardless of having a LED display would be the former, much like the older HP (CV/CC) supplies, or quite possibly the "fuse limit" where if the current is exceeded where it would shut the supply off.

I don't know if someone likes the aforementioned computer controlled displays that would temporarily show the dialed limit (perhaps for 1 second or so) on the same display that shows the actual current draw. Otherwise it would be necessary to have three displays - one for current voltage setpoint, one for current setpoint, and one for actual current draw...or a toggle switch.

[Longbow]

Re: Adjustable DC bench supply question

The "older" HP supplies demonstrate the need to short out the output in order to set the current limit. "newer" computer controlled supplies could double-purpose the display to set the current limit without needing to short the output to set the current.

Well, that was certainly a sweeping generalization. The HP power supply division designed and offered a great many types for various applications. They are not all the same by any means. The supplies range from simple unprotected models without any current limit or safety crowbar, to lab grade supplies that features remote operation, remote sensing, current crowbar AND automatic CV/CC switch over WITHOUT shorting the output. (I'm not getting the importance of why the setup is so important anyway.) These are some of the most reliable supplies which used only top quality parts on gold plated glass pcb's. The manuals and parts lists are available and the supplies usually sell for a small fraction of their original cost. I recommend having a closer look at these older HP supplies while also evaluating the requirements of the user. Finally, just because a digital disiplay might readout to a mV resolution, doesn't mean that the supply actually has the ability to select and hold its output to that precision. It is rare to actually require this level of precision for bench or lab use.

[eccerr0r]

Re: Adjustable DC bench supply question

Yes all the older ones you do need to short out because they do not have computer control. Old as in really old, pre-1980s - You would have to have three meters (three total - two current and one for voltage) to do this and it still is less accurate than shorting and using the same meter.

You could get close by setting the control knob graduations which usually are labeled but not always (I have a pre-HP acquisition Harrison Labs that does not have it labeled).

The preset capability is a "new" feature available with microcontroller control.