Lauter Grant

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Permalink Reply by mattd2 on October 18, 2012 at 2:04pm

The 30A rating seems like overkill for a home brew pump, mines "big" and it is only 80W or 0.33A. That could explain the high cost, plus shipping looks insanely expensive (even when split).

Depending on how much DIY you want you could do it with a couple of float switchs and a relay (high level float switch close the relay, relay is latched until low level float switch breaks the latching)

Some ideas for the float switches (I like the style in the first link personally): http://www.ebay.com/itm/CR-Horizontal-Tank-Liquid-Float-Switch-Wate... or http://www.ebay.com/itm/Sus304-Stainless-Steel-Curve-Water-Level-Se...

 As long as you rinsed off the floats after brewday I can't see much issue having them in the grant over some probes.

Just saw this one - http://www.ebay.com/itm/Double-Stainless-Steel-ball-Vertical-Liquid...

You could mount it through the bottom of the grant and get away with "1" sensor?

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Permalink Reply by Nick T on October 18, 2012 at 2:33pm

Thanks Matt and Guy, I would really like to pursue that as I only came to the expensive controller board because I could not figure out how to use normal relays to do this (call me thick), but can you explain how you 'latch' a relay? Or point me to a source of info on that? Do you use something like this?

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Permalink Reply by mattd2 on October 18, 2012 at 3:30pm

Guy makes a good point on limiting the use of 240V for controls circuits. If you did use my 240VAC circuit below you should be aware that you have 2 more points where you could potentially have a live pot! Make sure you have a very good ground coonection to everything that could potentially be at 240V and use a RCD.

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Permalink Reply by mattd2 on October 18, 2012 at 4:07pm

All good points for using low voltage DC over mains AC. Really up to 2A for the coils? The Omron datasheet says only 112mA for the 12V coil (+5 mA for the LED if it has one)

Datasheet

How many amps is the 12V power supply you have in your photos? and what did it cost? Link?

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Permalink Reply by Nick T on October 18, 2012 at 4:42pm

Ok, the omron relay and the float switches are ordered, thanks fellas for the info. Now all I need to do is get my head around Guy's circuit diagram and how it relates to the connectors on the relay, while waiting for the shipment (I like the idea of 12v near liquids!), get some weldless bulkheads for the grant vessel, get a grant vessel, 12v power supply etc and I'll be in business! 

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Permalink Reply by Nick T on October 18, 2012 at 5:02pm

Hey thanks for that, no rush!  Enjoy the drams. 

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Permalink Reply by Nick T on October 18, 2012 at 6:38pm

Thanks Guy for the speedy diagram!  I have been drawing over it and have finally figured out why the circuit remains live even though the upper float switch is off - that had been troubling me all afternoon, I hate not understanding these things....

Permalink Reply by Haish on October 18, 2012 at 9:50pm

I made this circuit for my grant. Etched a PCB and managed to squeeze it all into a jbox that mounts on the outside of the grant. I also used 2 curved float switches as in the link above. A 3 position dpdt switch gives manual on - off - auto (float switch activated) and also controls an RGB LED that changes colour to indicate the mode.

Permalink Reply by Nick T on October 19, 2012 at 12:13pm

Amazing - thanks for that, order placed! Much cheaper than getting a 12v wall power supply from jaycay and cutting it up to go into a box. And easier too!  

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Permalink Reply by mattd2 on October 18, 2012 at 3:24pm

Depending on if the floats are rated for 240VAC you have 2 options (see below).

With 240VAC floats you can control the relay (pump) going on with the high level float (normally open), then tie the 240VAC from the relay's contact back to the coil input through the low level float (normally closed). This way when the level reaches the high level the relay will turn on and stay on until the level drops below the low level when the relay will drop out... and then the cycle starts again.

For DC volatge floats you would need a double pole relay, one contact is for the pump the other for the latching circuit.

Someone might need to confirm this but I thought that AC loads where less harsh (for want of a better term) than DC loads on switch contacts so the floats I linked to above might be fine with the simpler circuit... again can someone comment on that?

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