Electronics > Beginners

Powering battery operated devices with bench supply.

(1/3) > >>

registereduser:
Just wanted to double check before doing something regrettable.
 
I have a TI-30Xa calculator with dead batteries. 2 @ 1.5v buttons of type GPA76.

It occurred to me to just wire it straight to the 3.3v on my improvise ATX bench supply. I have two concerns.

1. Will the calculator take care of current limiting itself, or do I need to include a resistor. If I do, what value?

2. Is the 3.3 OK, or do I need to drop to  3v?

floobydust:
I recommend using a current-limiting resistor, like 47-100 ohms.
I have had some devices latch up and die because the PSU was more powerful than a battery and the voltage rise was too fast when I connected the leads.

You can use a series Schottky diode to drop 3.3V down to 3V. We don't know what the calculator is rated for. EPX76 silver oxide batteries can be 1.6V max.
Maybe use some AAA batteries or something less scary than ATX PSU.

registereduser:
Sounds good. I tried to find info on the power needs online with no success.

I'm not too worried about using the ATX, with your suggestions. Thanks for the input.

JoeO:
No one can tell you since no one knows the characteristics of your improvised ATX power supply.  Does it overshoot?  By how much?  For how long?
No one has tested the calculator and specs don't exists to tell you for how long the calculator can withstand the unknown output of your power supply.

If you go to a local store, the cost of the batteries will come close to or exceed the cost of the calculator.  Presently they sell for $8.69 on Amazon.

Good luck!

registereduser:

--- Quote from: JoeO on January 13, 2019, 09:47:31 pm ---No one can tell you since no one knows the characteristics of your improvised ATX power supply.  Does it overshoot?  By how much?  For how long?

--- End quote ---

What is meant by overshoot? How can I determine those things?

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod