Poor Man's Flow Switch

[Maritimer]

CardinalBags has turned me on to flow switches, but they are expensive. Here is an idea that I might develop into something useful.

I took an scrap of plastic and hot-glued it to a microswitch. My coolant is recirculated by a pond pump, so I put a little clamp on the tube feeding back to the reservoir to make the water come out with some velocity. With the microswitch acting as the pivot for the plastic, and holding the microswitch in the correct position, it is possible to activate it with the water flow.

Flow switch not activated

Flow Switch Activated

[heartcut]

Good low-tech idea. Put that right up on the nozzle and try, might give you better repeatability, long as it doesn't splash the switch.

[Maritimer]

Here is a version that protects the switch from the water. The action is very positive.

The water enters through a cutout.

Without any water, the container is positioned so that the microswitch is almost activated.

With water pushing against the other side, the microswitch is closed.

M

[mash rookie]

Hi Maritimer.

I do like your electronic approach to things. You are thinking out of the box.

I am not understanding the use for a float switch? Is it controlling a servo to keep your bucket full? If you use it for your coolant pump wont you have temp swings on your condenser?

Can I borrow your idea for my gravity feed continuous stripper still?

MR

[Maritimer]

Hi MR,

Sure, borrow away.

The switch is to monitor coolant flow. The most dangerous thing about distilling is that you can get ethanol vapours in the air if your coolant stops flowing for some reason. I'm in the process of making a very safe still, and coolant flow is one of the things I want to sense.

M

[Cardinalbags]

Now we just have to start working on the iPad app for the corresponding alarms!!!

My home security system sends me emails when certain things happen. Ive been thinking about using a relay on the security panel to be tied into the flow switch to trigger an event.

Nice job on the flow switch by the way. Good implementation at low cost.

[bellybuster]

Cool idea, I don't think I ever have enough flow to activate that though

[Maritimer]

Hi bb,

I'm working on another design that uses gravity. A little cup fills up from the flow and activates the microswitch. The little cup has a little hole in it, so it drains if it isn't constantly filled. When there is sufficient flow, the cup overflows, keeping the microswitch activated.

M

[Maritimer]

Hi cb,

Can your security system send a telephone message? You might respond to that faster than an email.

M

[bellybuster]

not being a rainer on your parade but if you want to know your cooling is adequate why not measure temp of your distillate. Temp is easy to monitor and easy to use in automation. You can also set for specific temps to trigger an alarm/event.

It would be easy to say.. shut down your heat at 150 degrees distillate or ring a buzzer or whatever.

Still a cool idea but there are easier ways.

[Dnderhead]

here we go again...

[thecroweater]

not being a rainer on your parade but if you want to know your cooling is adequate why not measure temp of your distillate. Temp is easy to monitor and easy to use in automation. You can also set for specific temps to trigger an alarm/event.
It would be easy to say.. shut down your heat at 150 degrees distillate or ring a buzzer or whatever.
Still a cool idea but there are easier ways.

Your kidding right?
(if not) Have you done any distilling yet if so maybe whack that puppy in park and zip be to the beginners reading lounge to find out why that comment makes no sense bud

[Prairiepiss]

not being a rainer on your parade but if you want to know your cooling is adequate why not measure temp of your distillate. Temp is easy to monitor and easy to use in automation. You can also set for specific temps to trigger an alarm/event.
It would be easy to say.. shut down your heat at 150 degrees distillate or ring a buzzer or whatever.
Still a cool idea but there are easier ways.

Your kidding right?
(if not) Have you done any distilling yet if so maybe whack that puppy in park and zip be to the beginners reading lounge to find out why that comment makes no sense bud

Maybe you should read his post better.

He is suggesting taking the temp readings of the product coming out of the still. If you lose water flow to the product condenser. The temp of the product coming out will rise. And be a good indicator you have lost coolant flow. He is not saying you could control the still with it. This would be good for all stills except maybe an LM still. It would be a little different unless you had a product cooling condenser.

[thecroweater]

hmm apologies if that is whats meant, going by the OP it likely was but I don't think it would be any more accurate than a flow meter as I've always found the output temp is effected by flow and temp of the coolant verses the output rate. The output rate I've found can vary drastically by effective energy input verses ABV of the charge and effective energy can vary due to external environmental factors. Such a sensor would be really difficult to calibrate I would think and really need to be done specifically for each individual run , how you would calculate that I have not the slightest idea

[bellybuster]

Hmmm, handle is just about perfect..... Actually reading a post is usually the preferred route prior to flying off. No worries.

Output rate?? Where did that come from.? Who's talking about output rate?
Accuracy was never even mentioned nor is it required for this application. Temp vs flow to me is a no brainer, temp is so easily measured and very easily used as a control measure. Cheap, off the shelf parts and pieces.

As I said, cool idea and run with it, why not? Just puttin another idea out there.

[Maritimer]

My project is to make a very safe still. By very safe, I mean that there is a lot of redundancy in looking for problems. You might remember the inimitable cholme, who had his thread shut down by Rad. cholme is an expert in safety, and he has been mentoring me in this project. Redundancy doesn't mean only having two or more sensors watching one parameter, I learned; it ideally requires two or more different ways of sensing that parameter. So, bb, I am indeed watching the temperature of the reflux condenser case and also the temperature of the vent. I'm implementing my instantaneous reflux ratio measurement, too, so the operation of the still will be well monitored. There are other temperatures being monitored: the vapour temperature, product temperature, boiler temperature, and ambient temperature.

So here is a model of the bucket flow switch:

There is a little hole (1/4") in the bottom near the front. The little compartment in the front fills with water.

Here it is filled:

Here it is draining:

M

[heartcut]

Good stuff, Maritimer. I have a two level temp alarm on my product out and think about a audible alarm and a propane shutoff valve, but so far thinking is all I've done. The little amber and red lights have alerted me a time or two, a bell or a recording of hippos having sex would be more of an attention-getter.

[Maritimer]

Hi heartcut,

I'm interested in any safety or warning systems that people are using. Can you describe a little what the lights measure and mean? How serious is the problem when the lights light?

M

[heartcut]

It's a standard PID temperature controller, with a PT-100 RTD in the cup of the parrot. Primary purpose is correcting the proof annd trailles, but it comes with two programmable alarms and a couple contact outputs. I don't use it for control, so the contacts could be used for the stuff I mentioned earlier. The low alarm is 110degF and the high is 120, both of course adjustable. Easy to find in the $25 to $100USD range and real handy. Mine are pretty old, but still work. Some models come with one or more discrete inputs, which might fit into your control scheme as a place to connect your flow switch(s).

[Cardinalbags]

Lets not forget the purpose of monitoring flow. It is for detection of cooling water loss which is probably one of the biggest dangers we face regardless of whether you are there watching the still or leaving it unattended for 5 minutes while you take a bathroom break.....

Some have suggested monitoring still distillate. output temps, however that goes against rule number one in automation. If you can directly monitor the thing you wish to monitor, do that before monitoring some other variable that could potentially be influenced by other factors.

In this case, Maritimer is concerned about loss of cooling water, so measure directly against that. He is getting a digital signal via the on / off nature of the flow switch. Direct electro-mechanical control is highly reliable especially if the circuits are arranged properly.

I think he has developed a very good low cost solution here. No more than $20 worth of parts if you include a relay for taking that microswitch signal up in voltage for direct power cutoff to the boiler. Then again maybe that microswitch is good inline at the voltages of his boiler which makes the solution even more economical.

[heartcut]

Cardinalbags (great name, by the way), the primary hazard being measured is high output temperature approaching the vaporization temperature. A good indirect way to predict this is measuring the coolant flow. Either would make the still safer, both even better.
Those little micro switches are pilot duty for all practical purposes. I'd suggest an interposing relay, the inrush current of a solenoid would most likely burn out the switch contacts fairly quickly.

[Cardinalbags]

Cardinalbags (great name, by the way), the primary hazard being measured is high output temperature approaching the vaporization temperature. A good indirect way to predict this is measuring the coolant flow. Either would make the still safer, both even better.
Those little micro switches are pilot duty for all practical purposes. I'd suggest an interposing relay, the inrush current of a solenoid would most likely burn out the switch contacts fairly quickly.

Thanks, the spirits moved me to pick that name

I guess that depends on your particular use for it. In my case, i was running an LM still with a product cooler when i first put a flow switch in place. I lost cooling water and in the few minutes i was away from the still, i started filling my garage with ethanol fumes out the top of the primary condenser.

On the microswitch side, i agree the safest is the relay rated for the full load conditions. I have come across quite a few microswitches however that would handle the loads, mostly industrial grade ones however used in big industrial laundromats. Any component you use on your system should be rated for the full load conditions, but thats an up front design issue. Just grabbing something off the bench and using it is not always the best path!!

[Maritimer]

I'd like to see flow switches become standard paraphernalia on stills. Just for fun one day, I turned off the coolant on my pot still and lit the vapour. It came out like a blow torch. that taught me total respect for ethanol vapour.

I control four 1000W teakettle elements with a microcontroller, so for me the microswitch is all I need. Most people seem to be using thyristor power control. The microswitch could be put in the thyristor gate circuit without overtaxing it, me would think.

M

[Andy Capp]

So you needed to ignite ethanol vapour to learn that it's flammable?

[cholme]

So you needed to ignite ethanol vapour to learn that it's flammable?

No.............He needed to light ethanol vapour to find out exactly what would happen, yeah we know, flames but that's not exact is it. Why did he need to know exactly what would happen? You can't design effective safety measures against events you know very little about. For example, if the flame was just a little pilot light type of thing then it could be extinguished by a few seconds of water spraying across and into the vent. but that aint gunna work if you want to put out a blow torch

I like the idea of the slowly emptying flow switch, it removes the need for pressurising the output, In the past i have made flow switches which where to sense water in a ditch. This ditch was on a model of an industrial process used for red/blue teaming in the SCADA security world. If red team penetrates the system then the plant overflows and water flows down the ditch signalling the end of the contest. I made a capacitive sensor which is similar to those touch sensors found on PCBs. This was buried under several layers of paint and other water proofing compounds but still worked very well.

[RonH3154]

Anyone using this type of circuit to shutdown their still should disconnect it from its source of power ie gas or electrical.

If you use propane or natural gas then there should be an appropirately sized solenoid that would be energized (normally closed valve held open) to allow gas flow to the burner. The flow switch would then deenergize the solenoid on loss of flow. Also loss of power, a broken wire, or a failed switch should deenergize the solenoid.

If you use electric heating elements there should be an appropirately sized contactor that would be energized (normally open contacts held closed) to allow current to the elements. The flow switch would then deenergize the contactor. Also loss of power, broken wire, or failed switch should deenergize the solenoid.

[Maritimer]

Hi RonH,

That is exactly how my system works, urr, will work. As others have pointed out, the microswitch might be a little weak to take on a contactor. The one I've used is Alco 1478670-7 which you can see here: http://www.tycoelectronics.cz/catalogue ... 309227.pdf" onclick="window.open(this.href);return false;" rel="nofollow
It is SPDT, 0.1 amp 125VAC or 0.1 amp 30VDC with an operating force of 35g and a releasing force of 6g.

A typical contactor http://relays.te.com/datasheets/Model_9 ... series.pdf" onclick="window.open(this.href);return false;" rel="nofollow would require too much inrush current to use with this switch.

However, a solid state relay would be able to work within the ratings of this switch. Or the microswitch could drive an SSR which would drive a contactor, which is what I intend to do. (A microcontroller will drive the SSR which will drive the contactor.) Do you have a particular reason for not using an SSR instead of a contactor? Personally, I feel safer with a contactor, but is there some loss of reliablity in replacing a contactor with an SSR? I see from your profile that you are an engineer.

M

[heartcut]

An SSR would work. Be sure to use an appropriate diode, snubber or whatever the SSR manufacturer recommends for the power you're switching and use a heat sink of some type, maybe just a piece of sheet aluminum. It's unlikely that an SSR holding in a contactor or solenoid would fail, but keep in mind that SSRs can fail closed- best to check the operation each time before firing up the heat.

[Maritimer]

Got it. Fail closed.

M

[RonH3154]

Got it. Fail closed.

M

It can fail closed but you DO NOT WANT AN SSR TO FAIL CLOSED IN THIS SITUATION!