Re: i need simple water level indiactor
Hi,
Can I ask why you need the circuit? Unless the radiator is faulty/leaky and you (like many others at one time or another) have to keep stopping to fill it with water before it runs/burns dry, this sounds like app-itis - If you don't really need it, but you do need a timely reminder, an alarm on a mobile phone is a far less complicated solution to trying to measure a liquid level that rises and falls, gets really hot, is a circuit with twists and turns of different widths here and there, will not appreaciate any little part breaking or blocking something (I can visualise thet latter with far too much ease)...
It sounds like a fun challenge to contemplate but beginning to seem like an ATEX level circuit. Sorry to sound negative, I think an alarm on a phone or a cross marked on a paper yearly calendar is far more efficient (and sensible) here. Would using a temp sensor glued to the outside of the expansion tank be some way of inferring anything? I doubt it, but just to suggest something other than buoys or wires in boiling antifreeze... Good luck, though, it's a genuinely interesting design proposition.
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Where possible, I think this should be approached as an external design, if possible - you get rid of loads of problems at once. The expansion tank is usually transparent, isn't it? It has been in cars I've seen. Long (desperate) shot: If the tank is transparent and the antifreeze is opaque enough in colour, maybe an LDR on one side and an LED (sorry, but it's an idea) on the other, to trigger a comparator when the car basics are turned on if the LDR passes a voltage, for example; if so, I'd set it to trigger the comparator on a lower than Vref signal to trigger the beep or an LED near the dashboard, etc. I'm guessing not all car radiator tanks are transparent plastic, maybe. Also, shame a magnet in a floating ball or fixed into a track inside the tank (like kettle design to show water level) and a reed relay on the outside can't be done.