Hi All
Thought I'd put up some pix of my simple coolant flow sensor design.
The idea was to have a detector that wasn't inline with the coolant line and couldn't restrict the flow if it jammed up. Bad experience of these things in industry caused me to to design something that worked in the open flow of the system.
The sensor was cut from some scrap 6mm acrylic - a length of 2mm dia stainless rod for the shaft and three 8mm neodymium magnets let into the impeller (the drawing marks the centres, drill them 3mm deep with a bullet drill). Detector is an old hall effect switch (looks like an e-line transistor) - each time a magnet passes, the switch comes on. I initially tried the system with a reed switch, but the reeds I had were non too sensitive - YMMV. Any old hall effect switch like this should work fine - you'll need to rake through your local suppliers catalogue.
One side of the sensor is tapped to receive the three M4 stainless screws with a bit of plastic spacer tube to keep them apart (mine happened to be a scrap bit of outer sleeve from a sullivan pushrod - model a/c pushrod). I did cut acrylic spacers for the first model, but if you cut them from the same sheet, they're going to be the wrong thickness
The centre hole on the impeller needs to be drilled accurately at 2mm and the inside faces of the outers need to be again drilled partially through to trap the ends of the shaft - the 1mm holes act to allow water into the joints. A couple of wee plastic washers on the shafts will keep the impeller roughly centred - I used old transistor mounting bushes - you want a 'rattling fit' so that the impeller doesn't jam.
The sensor was wired up to a length of three or four core security cable - heatshrunk to the sensor legs, then the whole end dipped in clear model aircraft dope a few times - giving ten mins between 'coats' - to keep the water out. I guess I could have used silicone sealant, but I was in a hurry and silicone is messy - I've used dope a few times before and the method works just fine. The sensor was held into the rectangular hole with a 'popout' of acrylic from something I had been cutting before - I keep a scrap box of all the bits that end up on the crumb tray under the laser cutter - they eventually come in handy for something
The output end of the coolant pipe from the laser is simply tywrapped to the sensor assembly and wire so that the pipe is directed at the impeller. The hall effect switch runs from 5V, so you can connect it to any monitoring system - I like a simple approach and just use an LED attached to a resistor - the LED flashes to indicate flow - no fancy litres/min arduino/picaxe, I just want to know that it's rattling round
The whole assembly is just dunked in your coolant reservoir/bucket/container - if the impeller jams up, it doesn't restrict the coolant flow and won't cause any overheating probs. Of course, you can connect the sensor to anything you like - calibrate the whole gadget too if that's your thing (but in that case, you probably own a fancy Acme Inline Laser Coolant Monitor Detector with dilithium crystal inserts at the correct operating frequency
)
Cheers
Neil
- Flowsensor 1
- Flowsensor 2