[Coco] MC-10 Questions...

[KnudsenMJ at aol.com]

In a message dated 8/7/04 9:09:35 PM Eastern Daylight Time, farna at att.net 
writes:

> The other gauges, fuel level, engine temp, oil pressure, and possibly volts 
(
> haven't figured out how to do that one yet, the other three are simple 
> variable resistances that I know the ranges for) could be slower. The oil 
> pressure will have a back-up warning light. The numbers displayed will have 
> to be on a graphics screen to be big enough to easily see. I'd probably use 
a 
> mechanical hour meter under the hood and forget mileage, unless I can find 
a 
> stand alone odometer instead of an hour meter. 
>  
>  Heck, I've forgot how I measured resistance now!! I remember using the 
> joystick D/A inputs, but that's all. Got the idea from a game that used a 
> series of push buttons for a Jeapordy style buttons connected to one port. 
I 
> think each button had a different resistance and the CoCo could tell which 
> button was pressed. Might have to have the gauges work in 5 or 10 unit 
> increments, but would be close enough. 

I think you're forgetting something -- that the Coco's joystick inputs 
measure Volts, period.  Resistor hookups are just voltage dividers of a known 
external reference voltage, into a dependent voltage that feeds to the A/D joystick 
inputs.

To monitor your car's battery voltage, which ranges between 12 and 15 or so, 
use a pair of fixed resistors to divide it by 3, so that range becomes 4 to 5 
V (remember, the Coco joysticks measure from 0 to 5 V, no more).

I think a competitor, maybe Apple, used a similar scheme to the Coco's, but 
had one of the resistors built into it, so the joystick was just a variable 
resistance.  Not nearly as flexible as our Coco (but then, what was/is?)
--Mike K.