water level sensor

[Michael GilliganParticipant @michaelgilligan61133]

At Duncan’s request … here are three more ray-traces, with the source at different distances from the Water-filled glass tube.

Sorry, I really can’t do dozens of these … but if anyone can give me the dimensions of the original sensor arrangement, I am happy to try these in my model.

MichaelG.

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The generation of the traces is easy … but getting them onto the forum is tedious !!

Edited By Michael Gilligan on 05/03/2021 20:04:13

[duncan webster 1Participant @duncanwebster1]

That looks like explaining the rugby ball shape. The distance from the outside of the glass to the actual source of light is not the same as the distance to the end of the LED, but when the water filled glass is touching the LED the image fills the tube as I pull away at about 6mm distance the image is round, then becomes more rugby ball same as empty tube.

More news when the transistors arrive, I'll bet you can't wait!

[John BaronParticipant @johnbaron31275]

Hi Duncan, Guys,

An old computer mouse will provide you with at least four IR pairs. Two on either side of the slotted wheel !

[Michael GilliganParticipant @michaelgilligan61133]

Posted by duncan webster on 05/03/2021 21:06:34:

[…]

More news when the transistors arrive, I'll bet you can't wait!

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Meanwhile … I thought interested readers might find this diagram helpful:

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It shows the typical beam pattern for a common ‘5mm LED’

… and, by implication, it also represents the acceptance angle for the specified photo-transistor.

MichaelG.

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Note: I linked the data-sheet for the PT in an earlier post.

[duncan webster 1Participant @duncanwebster1]

well the phototransistors turned up, so I've made a lash up test rig. The voltage display is just the drop across the transistor. 15mA current through a red LED, no idea of its part number, it was in the bits box.Low water gives high voltage drop and vice versa. I can easily knock up some electronics to switch a pump etc, and to notice if a wire has dropped off. However, following Fizzy's suggestion I contacted Clevedon Steam. He is working on bringing back the sensor which Cheddar used to supply, and is working out how to cope with the heat from the gauge glass. No point 2 of us competing, and I don't want to undercut his sales possibilities, so this will now go on the back burner for a bit. It's getting pretty crowded back there, but at least it might get me enthused to finish off the stationary boiler it's intended for

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the update, Duncan

… looks like a clear and convincing demonstration

… Did you ever hear back from the originator ?

MichaelG.

[duncan webster 1Participant @duncanwebster1]

Posted by Michael Gilligan on 14/03/2021 15:21:42:

Thanks for the update, Duncan

… looks like a clear and convincing demonstration

… Did you ever hear back from the originator ?

MichaelG.

I joined the RCME forum and sent him a pm, but he seems to have gone to ground

thanks for your help everyone

[Grizzly bearParticipant @grizzlybear]

Duncan,

That poor multimeter, please give it a bath, I'm sure it will appreciate it.

Bear..

[duncan webster 1Participant @duncanwebster1]

OK so I've given it a bath and now it doesn't work. Seriously I've wiped it down with IPA and it does look a lot better, (and it still works)

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