Variable speed controller

I'm looking to convert to electric. I currently brew 5 gallon batches. I would like to build an electric HLT/BK and use a cooler mash tun in between. I'm looking for the simplest setup, and was thinking of using an element plugged into a variable controller so that I could just install a 4500 or 5500 watt element and manually control the output. The cost difference between the high wattage and low wattage elements is a few dollars, so I would like to just go with a high wattage element to begin with in case I want to upgrade later. I would also like the flexibility of being able to plug into a dryer plug in case I move later.

Somebody was kind enough to point out this, which seems perfect, but is awfully expensive.

I was also looking at these, but they are 120V. There is one on ebay for 240V, but it is only rated to 8 amps.

Question time:
1) Has anybody put something like this together, and how did it work?
2) Does anyone have suggestions on components, or how to build a box like that?
3) I don't see myself doing much more than 5 gallons in the future, should I just go with a 3000W element and just go with on/off?

Thanks a lot.

Search for PWM, they can be built pretty cheaply. Look through this forum, there are lots of builds similar to what you want.

millsware said:

Somebody was kind enough to point out this, which seems perfect, but is awfully expensive.

Click to expand...

Before assuming that $144.95 is expensive, I suggest you do some shopping around on the net & do some price comparisons.

millsware said:

I don't see myself doing much more than 5 gallons in the future, should I just go with a 3000W element and just go with on/off?

Thanks a lot.

Click to expand...

This would be my advice, unless you add temperature control, the higher wattage will just improve your ramp time during heat-up. Elements are so cheap that there is no big set-back $ to try one and build as you go. Stick a 3000w in your kettle, a larger wattage in your HLT if you like and brew a batch in manual mode.

Lots of folks here build wonderful sophisticated electric systems, but the bells and whistles are really optional IMHO.

And of course you know to use GFCI!

What about this: http://www.stilldragon.com/diy-controller.html I used this SSR setup (Solid State Relay) with a PID to control how often the element is "ON" works great!

I just ran some 10 gauge wire from a 30A double pole GFCI breaker into the unit above then outputted from the unit into a 30 amp plug.

I plugin in my kettle/5500W 240V element and use the PID to control the "power" of the element. let me know if you have questions or want some pics?

fermenter said:

What about this: http://www.stilldragon.com/diy-controller.html I used this SSR setup (Solid State Relay) with a PID to control how often the element is "ON" works great!

I just ran some 10 gauge wire from a 30A double pole GFCI breaker into the unit above then outputted from the unit into a 30 amp plug.

I plugin in my kettle/5500W 240V element and use the PID to control the "power" of the element. let me know if you have questions or want some pics?

Click to expand...

That's a bizarre set up, and not what the OP was after.

The kegkits controller is actually the cheapest readymade that I have seen. I doubt Mr Hargrave is making that much out of selling them. The chunky locking socket would probably cost about $15 on its own. 4' is maybe a bit short for the cable but hey.

alien said:

That's a bizarre set up...

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Works great for my needs and was much less pricey then other options I found for variable temp control. A SSR simply cut's power to the element so for example if you set the PID to 50% it would allow the element to be on 1/2 the time, thus you have your variable power.

But yes I am also mostly unclear as what the OP wanted to accomplish.

Your own post wasn't that clear either. Sorry if I misunderstood it.

PID on manual control with an SSR sounds fine but accomplishes the same thing as the Stilldragon controller, so I don't see why you need both.

fermenter said:

What about this: http://www.stilldragon.com/diy-controller.html I used this SSR setup (Solid State Relay) with a PID to control how often the element is "ON" works great!

I just ran some 10 gauge wire from a 30A double pole GFCI breaker into the unit above then outputted from the unit into a 30 amp plug.

I plugin in my kettle/5500W 240V element and use the PID to control the "power" of the element. let me know if you have questions or want some pics?

Click to expand...

If I'm understanding it correctly that link looks like what I want.

To clarify, I would like to have one element in a kettle. I would like some kind of control knob that I could set to 100% to heat quickly, and then turn down to say 50% to maintain a boil. I don't want on/off 50% of the time, I want 50% power.

millsware said:

If I'm understanding it correctly that link looks like what I want.

To clarify, I would like to have one element in a kettle. I would like some kind of control knob that I could set to 100% to heat quickly, and then turn down to say 50% to maintain a boil. I don't want on/off 50% of the time, I want 50% power.

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alien - Sorry I was not clear, the Stillgragon in the link is just a PID + SSR + Housing. just one per heat stick I do not have two SSR.


millsware - If you do not want "I don't want on/off 50% of the time" then the link I posted is not for you, you would need some sort of rheostat to lower the voltage. As I did not set mine up that way I am of no help.

I can say the SSR route works super well! but I still need full power to boil, but I use less just to heat up the wort via sparging.

So "*Sensitive potentiometer for precise heater control" is not what I'm looking for? What is the difference between a potentiometer and rheostat?

Bump

millsware said:

So "*Sensitive potentiometer for precise heater control" is not what I'm looking for? What is the difference between a potentiometer and rheostat?

Click to expand...

A rheostat is a higher wattage potentiometer.

millsware said:

So "*Sensitive potentiometer for precise heater control" is not what I'm looking for? What is the difference between a potentiometer and rheostat?

Click to expand...

I suppose we should step back, what is your goal? It seems to me that you just want the ability to control your boil rate correct?

If so it seems to me your cheapest option is to go with a potentiometer/SSR (Solid State Relay) setup

They way this works is the power is routed through the SSR. The potentiometer also attaches to this SSR, you can use the knob on the potentiometer to control how often the SSR allows power to flow to your element. So at potentiometer level 50 your element is OFF 50% of the time and ON 50% of the time. It does not lower the voltage going to the element, but no matter I can attest that that method does work just fine. As far as I know if you want to lower the voltage (power level of the element) you will need something like a rheostat and that will get more pricey.

The link you posted for $144 HERE seems to also be a SSR setup, but I am not sure without looking inside the device. I went with THIS one as it was the cheapest package without buying my own parts separately.

So yes a potentiometer is what you want but that is just part of it, what it controls is what makes the difference such as a SSR, rheostat or something else.

I hope I am being clear if not please let me know! Or if someone else has ideas please feel free to share.

fermenter said:

The link you posted for $144 HERE seems to also be a SSR setup, but I am not sure without looking inside the device.

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This is a SSR phase angle type device.

A rheostat is usually an adjustable series resistor. Wire is wound on a torroidal support and a wiper, rotating on an axle through the center of the doughnut can be rotated to contact the more or less of the wire according to the angle to which it is set. The further from the hot end the wiper makes contact the more resistance is in the circuit. A rheostat has two connections. One end of the coil and the wiper.

A potentiometer is the same thing except that both ends of the coil are connected as is the wiper so there are 3 terminals. In the usual setup a reference voltage is applied across the ends of the coil (which in the small units you are talking about isn't made of wire at all but a flat, circular strip of some resistive material) and a desired 'potential', determined by the wiper position, taken off from the wiper terminal. For example, if a 12 volt source is placed across the resistor's terminals, 3 volts will appear on the wiper if it's position is such that 25% of the resistance is between the wiper and the ground terminal, 6 volts if the wiper is half way...

Thus a potentiometer and rheostat are really the same thing with the differences being in the role they are intended to play and the size which has to do with how much current is involved. Potentiometers (pots) are usually much smaller. Think volume control from the old days when radios had knobs.

The device with the pot consists of a couple of SCR's whose firing angles are controlled by a circuit which determines the firing angle from a voltage passed to it from the potentiometer. It is really PWM but the pulse is half a cycle of the line. For 50% power the SCR's each conduct 90 ° for a total of 180 ° which is half the 360 of a complete cycle.

Some systems will turn on for integer half cycle numbers to minimize noise and stress on the components. For 50% power they might be on for 50 half cycles and off for 50 the point being that they only turn on (or off) when they are not conducting (the voltage across them is 0). This is clearly just another implementation of PWM.

If all you want is 50 and 100% that is very easily arranged by putting a single diode in series with the power line with a switch across it. If the switch is closed the diode isn't there (shorted out) and power is transferred to the load on both half cycles. If the switch is open then power only flows on alternate half cycles and the power delivered is half.

The elegant way to do this is obtain a SCR/Triac.... system whose firing angle cycle ratio you can control via a 4-20 current loop or 0-5 volts and hook that up to a PID controller with 4-20 or 0-5 output. This gives you really smooth output power control. Much smoother than turning the power on for 50 seconds out of a hundred.

Search for "voltage resistance SSR" on ebay or amazon to find the phase angle control.
Mine was about $12 shipped with a heat sink. Add the enclosure, pot, and power cords.

Make sure your power source has a GFCI for safety.

Thanks for your input everyone. So what I'm looking for is a dial that I can set to a percentage, and the element will only output that much wattage. So a 5500W element set at 50% will "act like" a 2750W element. In older chemistry labs they have what are called variastats for controlling hotplates, and I was thinking of something like that. The variable speed router controls seem to do the same thing, but I can't find one at 240V and 20 amps.

For the SSR control, how fast is the switch between off and on? If I set it to 50%, does it switch on for 1 second, off for one second...millisecond...minute? If it is a fast switch, then it seems like it would effectively accomplish what I'm after.

This one will handle 20 Amps, easy.

http://www.ebay.com/itm/10000W-220v...Speed-control-Dimmer-Thermostat-/181048405275

alien said:

This one will handle 20 Amps, easy.

http://www.ebay.com/itm/10000W-220v...Speed-control-Dimmer-Thermostat-/181048405275

Click to expand...

Sounds a little too good to be true.

For the GFCI, can you just upgrade the outlet, or do you have to go all the way back to the circuit breaker?

I bought a 40A SSR with heat sink off amazon for $14 shipped. I swtch it with a microcontroller but there are other PWM circuits out there.

Standard 'dum pwn' frequency is adjustable if you build you own circuit. I don't know what frequency PID controllers use but if they are smart they use zero-crossing logic to switch integral numbers of cycles. Your minimum predictable possible on-time is 1/120th of a second in North America, so if you want to be able to turn your element down linearly-ish to 10% then your maximum PWM frequency is about 10hz. With 'dum pwm' that is not synced to line frequency its better to add a safety factor for glitch-free operation so i would suggest 2 to 4 Hz max freq if you are not detecting zero-crossings. You will have less switching losses by going even slower.

millsware said:

In older chemistry labs they have what are called variastats for controlling hotplates, and I was thinking of something like that. The variable speed router controls seem to do the same thing, but I can't find one at 240V and 20 amps.

Click to expand...

Ah, yes, the old Variacs. They still make them and as they are auto transformers they will step up voltage as well as down so that you could, for example, run a 240 V 20 amp heater from a 120 V 40 amp circuit (it you had a 120V 40 amp circuit). But you won't like the price of even a small Variac. The heating mantel control function in a chem lab these days is now managed by a much smaller and lighter (and much less expensive) little box with an SSR and a proportional controller (really just a timer as there is no temperature feedback) in it.

millsware said:

For the SSR control, how fast is the switch between off and on? If I set it to 50%, does it switch on for 1 second, off for one second...millisecond...minute? If it is a fast switch, then it seems like it would effectively accomplish what I'm after.

Click to expand...

As I noted in my previous post there are several ways to skin this cat. A PID controller will let you select the cycle time you want. I use steam so I set it pretty long (30 sec) to reduce the number of operations of the steam valves. A SSR shouldn't be subject to 'wear' (if properly designed i.e. to only switch at 0 crossings) and so you can go to much shorter cycle lengths. A phase angle system fires 120 time a second (in the US). Keep in mind that your load in brewing has a big thermal mass. Temperature recordings made in my system do not reveal the 30 second cycle length.

Not to highjack your thread but...

I am looking at the same setup. Mine will be two kettles. The only difference is I would like to have a three way switch (on-off-on) which would allow to me to select between the two elements/kettles and have a light for each on the box to indicate which element has power.

Would that basic still dragon PWM control box work my design and just add the switch and lights? Or will I need a second SSR?

Thanks
Steve

alien said:

This one will handle 20 Amps, easy.

http://www.ebay.com/itm/10000W-220v...Speed-control-Dimmer-Thermostat-/181048405275

Click to expand...

It looks like the heatsink is not large enough and they even note this in their listing.

"Note:
the load cannot exceed the specified maximum power, please pay attention to the temperature at first use. if the temperature too hot exceed 80 °c, please enhance heatsink, or would burn out module and load.
if connect to inductive load or Capacitive load, the power must leave Two-thirds (2/3) margin."

The heatsink is in fact pretty huge. 20 A is half the rated current of this controller - it is more than adequate to control a 5500 W element. I know several people who have been doing so successfully with no problems.

But then you are selling a competing product at a higher price. If I was being uncharitable I might assume that you have an interest in slagging cheaper competitors.

alien said:

The heatsink is in fact pretty huge. 20 A is half the rated current of this controller - it is more than adequate to control a 5500 W element. I know several people who have been doing so successfully with no problems.

But then you are selling a competing product at a higher price. If I was being uncharitable I might assume that you have an interest in slagging cheaper competitors.

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I can't stop you from believeing what you want.

But I bought one of these to see if it would work in the controllers I was designing. It would have been much easier to just mount completed $20.00 assemblies in boxes than to assemble the design I come up with. I decided against them because when I tested the one I bought, the heat sink got very hot with a 5500 Watt elemant and I saw no way to mount a cooling fan in a location that could not be covered up by the user.

But the sample was well built and as long as you provide cooling one of these should work fine.