Friday, May 04, 2012
A little local difficulty - solved
Here’s my mark 1 circuit for Herbie’s proposed water tank gauge. Neat and tidy huh? I like it. In fact I’m really pleased with it. There is one tiny problem though. It doesn’t work.
Well it is only mark 1. I need to probe around with a meter to see if I can spot why. My suspicions fall in two places at the moment. 1. the integrated circuit (the black lump in the middle)– have I damaged it electrostatically? That could be 40p down the drain (don’t tell Kath), or 2. the resistor values might need to be changed. Although I got the circuit working on the prototype breadboard, I did change the resistors when I came to the soldered circuit (I thought for the better).
So I blunder on, not really knowing what I’m doing, but it’s cheap and it’s fun. And you never know, one day it might work.
A few hours later . . .
Yeeehaa!! It works. I had (stupidly) omitted a couple of little earth wires on the circuit board. Now connecting sensor wires to the terminal blocks and dipping them in a pot of water, all the lights come on. I suppose I ought to test it in a larger container, but I reckon it'll be fine.
So that's the guts of the thing done. Now I need to make the actual 5 wire dipstick to go into the water tank and somehow get it to resist condensation or I'll get false readings. Then I have to connect it all up with a switch and put it in some sort of casing. I expect that'll be a pain too.