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Full Version: HP41: Power Consumption on Devices. A question.
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I do not have a precise ampmeter to get the results and there is a possibility of these data already exist. So, the questions are: to have a comparison between both Card Reader and Optical Wand for the HP41, I would like to know
- how much current does the card reader need to read a card?
- what is the current increase when the wand`s LED is lit?

I know there is no direct comparison unless a barcoce sequence equivalent to the complete contents of a magnetic card is read. I just want to figure out if reading barcodes is less power consumption than reading cards. For low amounts of data there is no doubt about it, but concerning to batteries life, when one has to save long programs for later use, what is best: recording them on magnetic cards or printing barcode sequences?

Thanks for any info. Maybe there is some sort of e-doc about it, and poiting a link would be of help, too.


The card reader motor draws around 150-200 mA (for about a second). The wand LED around 20 mA. Unless you can read your bar codes in less than 10 seconds the card reader is probably best. However the small N cell batteries can better deliver 20mA when they start to run down. You can still use the wand long after the card reader stops running.

The card reader draws surge currents of about 1A (yes 1 amp!) from the batteries when the motor starts.

The information you posted is valuable! Thanks a lot.