Friday, May 04, 2012

A little local difficulty - solved

P1060041 (1024x768)
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.


Simon said...

almost certainly sucking egg territory, but do check all track breaks in the stripboard are really breaks - it's easy to leave one side connected.

After that, prod around with the voltmeter and make sure you've got what you expect at each point; after that it's bound to work, surely? ;-)

Simon said...

not fair! I don't get to edit my comment! ;-)

glad all going now. Been thinking of a simpler version - just one signal, that indicates whether the water is above or below a certain level (i.e. 1/4 or 1/3 full)...

Halfie said...

I think you've just done the easy bit, Neil.