Auto-sparge via liquid level sensor on site glass - Project
 

Just started this build and hope to get some input on the design, mainly need to make sure I have the right relay (see schematic).

Background
I typically take 45-60min for a 5 gallon batch to sparge and up to 2 hours for bigger batches. Adjusting the input/output of the sparge is tedious - I have better things to do than constantly tweeking the valves during this phase. I wanted to build an auto sparge system with the following requirements:

- Non-penetrating of kettle
- Measurement system that will not be in the mash kettle (cleaning, contamination, clogging)
- Easy adjustments
- Reasonably priced components

Solution
For the reasons mentioned above, I wanted to avoid the Blichman auto-sparge and general float switches.
I noticed on HBT that someone mentioned Omron had a site level sensor, but subsequent messages on HBT yielded no results of someone actually doing a build.

However, I was able to find the liquid level sensor from Omron (picture below):
http://www.ia.omron.com/products/family/475/
I have a Blichman 20gal tank and was able to remove the outer (metal) measurement guide. The site glass is 15mm so the E2K-L26MC1 was the appropriate size. These sensors are a NO operation mode. The premise is that they will turn on/off the pump, based on the level of liquid in the site glass. They are easily attached via small zip tie and can be slid up/down the site glass. They can be attached with a separation of >1 3/8" (>35mm), which is perfect for a liquid level bed.

Wiring
See the attached wiring diagram below. I am not sure about the correct relay since I cannot find a wiring diagram of one.
I will be controlling the pump on/off via the two sensors. The relay will be able to handle 120V output so an SSR is not needed.
If someone could help out with the appropriate relay, that would be great.

Cost
(2) used Omron E2K-L26MC1 = $40
(1) relay/base = $25
wiring/plugs = $6
Total cost = ~$71

Photo at bottom of page is existing setup (before any mod).

Can't you use a single optical sensor to turn a single pump on/off? Similar to a mechanical float switch.

Are the valves going to be at a pre-positioned level? at the full flow rate of a march pump I'm not sure how you would control cycle time.

The sensors are NO activated, so would need two: one for the higher level and one for the lower level.

They can be adjusted up/down on the sight tube. The gap between the sensors will dictate the cycle time. Here is a mock-up I did on the sight tube with the sensors (NOTE: will use zip ties instead of rubber bands).

I am just waiting for someone to check if I have the correct SPDT relay.:mug:

Subbed. I want to see this work.

I think you will need several additional components to create a dead band/historiesis with 2 sensors. If the mash drain and pump flow rate are pretty close then the cycle time should be pretty long.

Alternately you could cycle a solenoid valve on/off and leave the pump running.

JCO, thanks for your feedback.
The cycle time will be based on the separation of the two sensors. Since they are NO operated, I thought a SPDT relay would work well. It would basically toggle back and forth between on/off. The relay and sensor would be off of 12VDC to trigger the pump on/off. The relay is rated over 120V so I would run a leg through it for the pump.

I thought about doing the solenoid valve on/off, but did not want the pump spinning for that length of time.

Want to know if there is any relay experts out there to see if I spec'd the right one. It is McMaster-Carr #7266K41.

The McMaster-Carr #7266K41 relay is A-Ok. However I think you need to refine your wiring plan for the level switches and the way they will energize the relay.

OR - perhaps I just do not understand the wiring layout of the sensors. That (BTW) is most probable. I've not been able to find a single circuit diagram for them.

P-J

I love the idea of using these sensors on a sight glass! I'm not getting the logic of the wiring diagram, though. It seems like there's three possible states with the two sensors, and the desired behavior is:
1. Water below both sensors --> Sparge pump should be on
2. Water above both sensors --> Sparge pump should be off
3. Water between the sensors:
--> Sparge pump should be on if last state was (1)
--> Sparge pump should be off if last state was (2)

In your diagram it looks like you're planning to wire the switches in parallel, so the pump relay is engaged whenever either switch senses fluid. Is that right? If so, it wouldn't give you the history dependent behavior you're wanting in state (3). In fact, I think your pump just be off in state (1) and on in state (2) or (3).

But I'm new to electronics, so take this all with a grain of salt.

EDIT: Ignore me (the electronics newbie) -- P-J is on the case!