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The X-Philes (2nd Revision)
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The X-Philes Number 1 (1995).iso
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drain.doc
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1995-03-31
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(Comp.sys.hp48)
Item: 154 by dougc at bert.cs.byu.edu
Author: [Douglas R. Cannon]
Subj: HP48 currents for various operations
Date: Fri Nov 08 1991
I was playing around the other day and decieded that I wanted to know just
how much current the HP48 uses with different operations. Everyone is always
saying, "IR transmissions cause a great drain on the batteries..." or,
"Lots of number crunching will cause significant battery drain..." So, I
wanted to know how much.
In the hopes that this is interesting to others, I am posting a partial
list that I have begun to compile. These are simple operations that I was
able to think of in 10 minutes or less. If anyone has ideas for other
operations that should be tested, please email me. I would like to make this
list as complete as possible. Also, any comments, or questions are readily
accepted.
This is the current drawn from the batteries, given the operation:
Current | Operation | Other
( mA ) | |
------------------------------------------------------------------------
0.016 | HP OFF | probably not reliable
2.22 | idle |
7.0 | "normal" program execution | ( most programs )
7.0 | Stack manipulations |
7.0 | yat 1.0 ( Tetris... ) |
6.62 | BEEP | 600 Hz
8.84 | BEEP | 8000 Hz
8.85 | BEEP | 10000 and above
7.0 | XMITRM ( IR remote controller ) | 16.0 mA briefly
< 4.6 | Clock on in status line | fluctuates (2.22 - 4.6 mA)
3.6 | Command line input | idle
2.27 | Stack depth of 500 | idle
6.8 | Plotter | sin(x)
< 3.9 | Edit mode | ( 3.6 - 3.9 )
7.2 | Edit mode when checking syntax | or moving cursor
--------| WIRE TRANSMISSIONS -------------------|-------------------
2.22 | idle, port closed |
3.22 | idle, port open! (connected) | connected to a Mac
2.52 | idle, port open ( not connected ) |
8.15 | transferring to a mac | maximum
--------| IR TRANSMISSIONS ---------------------|-------------------
2.22 | idle, port closed |
3.22 | idle, port open (wire connected) | figure this out!
2.52 | idle, port open ( wire not connected )| this one too.
7.2 | Transmitting, trying to connect | couldn't test a real trans.
15.7 | Printing ( no printer near by ) | All time high!
--------------------------------------------------------------------
A couple of notes:
Pressing ON does not close the I/O port, but turning the HP OFF, then ON,
the port is closed. ( I guess the manual wasn't kidding when it said to
always close the port! )
Notice the clock. The ammeter showed a lot of fluctuation, but I am guessing
that HP draws 2.22 mA as normal, then each time an interrupt is received for
the clock, it momentarily draws around 4.6 mA.
--------------------------------------------------------------------
So that you can try this at home...
How it was done:
It was rather simple, of course. I just took out one of the batteries,
connected it back in with wires, placing my ammeter in series with the
batteries. Then, nervously, I turned it on. Since it didn't explode, I was
able to make the measurements shown. I feel that the measurements are good,
since the ammeter I used has only a 250 mV maximum burden at fullscale
of 200 mA. The only measurement I need to do more accurately is when the
HP is off.
---------------------
Douglas R. Cannon
dougc@bert.cs.byu.edu
---------------------