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5849 posts

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#272974 28-Jul-2020 14:06
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Is there such a thing as a prototyping board for 12v DC systems?

 

I've designed a pump control circuit, but I want to test it before I build it on the boat.

 

I immediately though of a breadboard.  Is there something similar but heavier duty - able to handle a 20A motor.

 

 

 

 

 

 

 

 





Mike

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  #2530155 28-Jul-2020 15:03
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Not that I know of but you can use a panel of non-bready actual wood which is where the name came from. That allows you to screw components down and make solid wire connections above the board.


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  #2530201 28-Jul-2020 15:28
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How many components?
On-off, limit switches, relays?
At 12v 20a I would use screw terminal blocks.
Have you developed a prototype schematic we can see for suggestions/help?




Gordy


 
 
 
 




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  #2530208 28-Jul-2020 15:45
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Gordy7: How many components?
On-off, limit switches, relays?
At 12v 20a I would use screw terminal blocks.
Have you developed a prototype schematic we can see for suggestions/help?

 

Hopefully the picture says it all (ignore the reference to 10v, it was the only suitable icon available).  Also note there is an error with the bypass switch - it should come off the master switch, not the relay control circuit: -

 

 

 

 

 

 

 





Mike

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  #2530252 28-Jul-2020 16:42
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That flyback diode will get very hot unless you turn it around :-)


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  #2530256 28-Jul-2020 16:49
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I haven't analysed what you are trying to do with your prototype pump circuit.

 

Total of 25 terminals.

 

Possibly 14 of the 25 would require heavier terminals for the 20amps.

 

Lighter terminals 11 of the 25 could be used for the control side where current is likely to be lower.

 

Either way a few extra terminals of each size should be allowed for looping and linking and for changes.

 

With the terminal blocks screwed to a piece of wood will allow you to pencil in labelling.

 

 





Gordy


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  #2530259 28-Jul-2020 16:58
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elpenguino:

 

That flyback diode will get very hot unless you turn it around :-)

 

 

OP is showing battery neg connected to the fuse and the main switch. It does therefore mean that the LED indicators are the wrong way around.

 

I guess OP should more clearly indicate battery polarity.





Gordy


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  #2530264 28-Jul-2020 17:07
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Gordy7:

 

elpenguino:

 

That flyback diode will get very hot unless you turn it around :-)

 

 

OP is showing battery neg connected to the fuse and the main switch. It does therefore mean that the LED indicators are the wrong way around.

 

I guess OP should more clearly indicate battery polarity.

 

 

That's right.

 

Rotate the battery symbol and attach the negative to an earth icon, or extend the wire to the far side of the diagram.

 

Then rotate the flyback diode.

 

 

 

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


 
 
 
 


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  #2530326 28-Jul-2020 18:49
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I think I'd aim to prove the concept with a 1A 12v motor using conventional breadboard before scaling up to 20A.

And add some resistors in series with the LEDs.

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  #2530333 28-Jul-2020 19:01
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I'd like to propose a correction that will give better lndication of bilge water.

Click to see full size

Hope it makes sense to you.

Edit: make sure your solid state relay is for DC load. An AC one won't turn off.




Electrician.

 

Location: Dunedin

 

 




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  #2530516 29-Jul-2020 08:47
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elpenguino:

 

That flyback diode will get very hot unless you turn it around :-)

 

 

I know! The drawing software doesn't rotate stuff.





Mike

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  #2530525 29-Jul-2020 08:55
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I'd use a re-settable breaker in an easy to get at / visible place rather than a fuse - stuff trying to dick around trying to replace a blown fuse on a bilge pump when and if you need it. If the breaker trips again straight away, then go find the bucket.  (I replaced the switchboard on my boat with all breakers a few years back.  On the very rare occasion fuses had blown, the process of finding the spare fuses in the dark, finding reading glasses so I could read the rating on the end of the fuse, looking to see if the fuse had actually blown, then replacing it (possibly twice - because there's a reason fuses blow).

 

 




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  #2530537 29-Jul-2020 09:25
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Fred99:

 

I'd use a re-settable breaker in an easy to get at / visible place rather than a fuse - stuff trying to dick around trying to replace a blown fuse on a bilge pump when and if you need it. If the breaker trips again straight away, then go find the bucket.  (I replaced the switchboard on my boat with all breakers a few years back.  On the very rare occasion fuses had blown, the process of finding the spare fuses in the dark, finding reading glasses so I could read the rating on the end of the fuse, looking to see if the fuse had actually blown, then replacing it (possibly twice - because there's a reason fuses blow).

 

 

I'm using a Narva fuse box that has built in a negative bus and two positive buses.  I really like these for system compactness, on a small boat. I haven't seen a spray proof marine circuit breaker switch panel that offers this.  I like toggle switches in my switch panels because the come in a variety of configurations that allow one switch to do two things.

 

There are circuit breakers that can be slotted into fuse blocks.  So that's a possibility, but doesn't address the issue of finding the right fuse in trying circumstances.

 

The boat has redundant bilge pumps on separate fuses.  I also carry a pre-plumbed and pre-wired spare.  It connects directly to a battery and the discharge hose goes over the back, held in place by passing through a tee that slides into one of the rod holders.  About 30 seconds to deploy if required.

 

 





Mike



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  #2530544 29-Jul-2020 09:40
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andrewNZ: 

Edit: make sure your solid state relay is for DC load. An AC one won't turn off.

 

It definitely is.  JayCar were very helpful.





Mike



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  #2530602 29-Jul-2020 10:29
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Gordy7:

 

I haven't analysed what you are trying to do with your prototype pump circuit.

 

Total of 25 terminals.

 

Possibly 14 of the 25 would require heavier terminals for the 20amps.

 

Lighter terminals 11 of the 25 could be used for the control side where current is likely to be lower.

 

Either way a few extra terminals of each size should be allowed for looping and linking and for changes.

 

With the terminal blocks screwed to a piece of wood will allow you to pencil in labelling.

 

 

The basics purpose is to reduce cable size by separating monitoring and control of the bilge pump from switching it.

 

The usual approach to switching and monitoring a bilge pumps is to do both from the helm (near front of boat), but on small boat the bilge pump is at the back (as is the battery).  So power is sent from the battery to the helm and back to the pump. Because this is 12vDC voltage drop is pronounced and you need quite big positive cables for the longer cable route via the helm if you want to limit voltage drop - a good idea on a critical system like a bilge pump.

 

A relay requires minimal power to actuate, and an LED require minimal power to illuminate. By controlling and monitoring from the helm of the boat while doing the actual switching with a relay at the back, the cable run is 90% shorter.  I save myself several cable gauges.  I can then use a standard double sheathed, 3-core marine cable (negative, auto and manual), which means I don't need a conduit, I can just secure with cable tie blocks at appropriate intervals.





Mike



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  #2530606 29-Jul-2020 10:30
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Updated circuit design ... figured out how to rotate stuff.

 

 

 





Mike

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