(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 ---------------------