The Museum of HP Calculators

HP Forum Archive 19

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82104A card reader current measurements?
Message #1 Posted by Eric Smith on 10 June 2009, 4:03 p.m.

Does anyone happen to have measurements of the current consumption of the card reader while reading or writing a card? Or the total of the 41 and card reader?

      
Re: 82104A card reader current measurements?
Message #2 Posted by marais on 10 June 2009, 4:16 p.m.,
in response to message #1 by Eric Smith

I only recall a measurement of the motor alone, between 7 and 9mA.

Andreas

      
Re: 82104A card reader current measurements?
Message #3 Posted by Michael de Estrada on 10 June 2009, 4:48 p.m.,
in response to message #1 by Eric Smith

I think you can hook up a regulated DC power supply with a DC ammeter in series to the battery terminals to do this. I have done this with a number of calculators, although never with one that included a card reader. You have peaked my interest so maybe I'll try it with one of card reader calcs (HP65/HP67/HP97). I own two HP41CV's but no card reader. I think they all use the same DC card reader motor, so I'd expect comparable current draw.

Michael

            
Re: 82104A card reader current measurements?
Message #4 Posted by Eric Smith on 10 June 2009, 5:25 p.m.,
in response to message #3 by Michael de Estrada

Yes, I could measure it myself, if I had a card reader. I don't, and thus the request.

                  
Re: 82104A card reader current measurements?
Message #5 Posted by Michael de Estrada on 10 June 2009, 5:56 p.m.,
in response to message #4 by Eric Smith

Here's some preliminary info based on a HP65:

Applied voltage at battery terminals - 3.75 Vdc

1) Calculator powered on and idle - display 0.00 - 140 mA

2) Calculator during a card read - 300 mA

3) Net current draw of card reader = 160 mA

Note that the current draw initially peaks as high as 450 mA as the motor does extra work grabbing the card and overcoming initial static friction (sliding friction is less). Also, I imagine this will vary between different card readers based on the tightness of the drive roller. If you are interested, I will test other calculators as I have 3 HP65's, 2 HP67s and a HP97. Also, all of these have been refurbished, so I have no baseline to the original.

Edited: 10 June 2009, 6:02 p.m.

                        
Re: 82104A card reader current measurements?
Message #6 Posted by Eric Smith on 10 June 2009, 6:15 p.m.,
in response to message #5 by Michael de Estrada

Thanks for taking those measurements. I'm assuming that the HP-67 measurements will probably be similar, and that will help with another one of my mad scientist projects that I hope to show off at HHC 2010. (I've got a different mad scientist project in the works that I hope to show at HHC 2009.)

      
Re: 82104A card reader current measurements?
Message #7 Posted by Eric Smith on 10 June 2009, 6:09 p.m.,
in response to message #1 by Eric Smith

Found the information in the archives, while looking for something else. Summary: 150-200mA continuous (while in operation), with peak current of up to 1A.

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv007.cgi?read=13849

            
Re: 82104A card reader current measurements?
Message #8 Posted by Michael de Estrada on 10 June 2009, 6:20 p.m.,
in response to message #7 by Eric Smith

Seems consistent with my results.


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