12v DC Prototyping Board??

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MikeAqua

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#2530612 29-Jul-2020 10:36

elpenguino:

Question for OP: can the pump operate dry with out damage?

Yes. Most small bilge pumps are centrifugal (self priming and tolerant of cavitation and small debris). They are usually either designed to tolerate running dry, or have run-dry protection built in (detects no load on impellor and stops).

The pumps I have can tolerate running dry.

Mike

MikeAqua

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#2530656 29-Jul-2020 11:01

andrewNZ: I'd like to propose a correction that will give better lndication of bilge water.

Hope it makes sense to you.

If I understand correctly, then the extra LED is detecting when the relay (or bypass) is closed?

Mike

andrewNZ

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#2530676 29-Jul-2020 11:48

No. I assumed your flyback diode was a lamp to say the motor was running.
I'm not convinced about the need for your flyback diode.

My change moves and rotates the auto manual switch so that you have indication of the float switch state regardless of the auto/manual switch state.

MikeAqua

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#2530682 29-Jul-2020 12:04

andrewNZ: No. I assumed your flyback diode was a lamp to say the motor was running.
I'm not convinced about the need for your flyback diode.

My change moves and rotates the auto manual switch so that you have indication of the float switch state regardless of the auto/manual switch state.

I've updated to use the correct symbol. [edit: I incorporated your idea around showing the state of the float switch. I'll be able to see whether the circuit has power and whether the float switch is closed. I'll have two of these circuits (one for each pump) and a third float switch on a separate battery (two outboards) that will trigger a piezo. One of the pumps will be in a higher position than the other two and the float switch controlling the piezo will be even higher. Effectively I'll have three levels of water detection].

I've read arguments for and against using flyback diodes with solid state relays controlling an inductive load, so I've erred on the side of caution. It would be simpler to not have the fly-back, but the relays were expensive.

Mike

andrewNZ

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#2530703 29-Jul-2020 12:54

If I was doing this, I'd also split the power and control, and put them on separate appropriately sized fuses.

So that:
If the control failed short circuit, the pump could still work and vice versa.
A control circuit failure would actually operate the protection.

ETA: I hope your solid state relay has a good heatsink.

MikeAqua

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#2530779 29-Jul-2020 14:26

andrewNZ: If I was doing this, I'd also split the power and control, and put them on separate appropriately sized fuses.

ETA: I hope your solid state relay has a good heatsink.

Good idea regarding fuses. I'll do that.

Good point on the heat, I'll have to see how much heat it generates. The SSR is rated to 100A, and I'm only using 32A.

https://www.jaycar.co.nz/solid-state-relay-4-32vdc-input-30vdc-100a-switching/p/SY4086

My plan was to put it in a sealed plastic housing and mount it on the underside of a plastic deck hatch. A heat sink will just heat up the air inside the enclosure.

I could use a die-cast sealed alloy enclosure and mount the SSR with the baseplate in contact with the enclosure.

Mike

andrewNZ

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#2530895 29-Jul-2020 17:38

The SSR will need a heatsink. It might not generate enough heat to overheat the box, but it'll probably generate enough to destroy the relay without a heatsink.

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Fred99

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#2531142 29-Jul-2020 22:41

Could save some drama if these would do the trick - at a slight premium over standard bilge pumps.

http://www.tmcint.com/en/product-213956/BILGE-PUMPS-AUTO-EYE-series.html

Handle9

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#2531168 30-Jul-2020 06:47

andrewNZ: The SSR will need a heatsink. It might not generate enough heat to overheat the box, but it'll probably generate enough to destroy the relay without a heatsink.

I'm curious why there's an SSR at all? Unless the pump switches on and off a lot it's an unusual device for motor starting. It'd be simpler and cheaper just to use a relay.

elpenguino

3424 posts

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#2531187 30-Jul-2020 08:23

Contacts, salt water, middle of the ocean .....

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

MikeAqua

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#2533448 3-Aug-2020 06:57

andrewNZ: The SSR will need a heatsink. It might not generate enough heat to overheat the box, but it'll probably generate enough to destroy the relay without a heatsink.

I'm thinking of using an alloy enclosure as the heat sink. The SSR has a metal base, which I think is what would normally contact the heat sink. Instead I could mounting the SSR with its metal base in contact with the alloy enclosure. The heat would then conduct into the enclosure and radiate. The enclosure will be locate below deck, which is a cool environment.

I could even mount the enclosure to the bilge pipe (also alloy). When the bilge, runs cold water will be flowing through that pipe.

Mike

MikeAqua

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#2533449 3-Aug-2020 06:58

Handle9:

I'm curious why there's an SSR at all? Unless the pump switches on and off a lot it's an unusual device for motor starting. It'd be simpler and cheaper just to use a relay.

I've tried mechanical relays in SW environment before, they tend not to last. Admittedly not in an enclosure, so that's a possibility.

I'd need to find another project for the two SSRs ...

Mike

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