Electrical questions +servos/actuators.

Hello all,

I'm in the planning stages to build a box housing controls for a home brewery and would like to know if anyone can wrap my head around some things. I need recommendations on a transformer to take the 240v ac coming into the box and convert it to 9v dc, 1 amp for the arduino. I would like to use a terminal block so the 240v can be used on 3 separate 240v ac heating elements. The heating elements are 5500w, 3000w, and 1000w. All told, the heating elements will need to be on at least a 40 amp circuit breaker. I figure with all the bells and whistles I'm going to want a 50 amp circuit breaker. I am also needing to power a 120v pump (the march ac-5d-md). I believe the pump needs about 2 amps.

Any recommendations on what to use/engineering concerns would be appreciated. I'm a little concerned about heat within the box if I've got that much juice flowing through it. (it is a 16x16x8 plastic box)

I'll be using the arduino to act as a PID, switching relays to turn the heating elements and as a control to turn the pump on and off as it also controls actuators for the valves.

I'm not yet sure what to use to control the swagelok valves, so any reccomendations on servos/actuators would also be appreciated.

You might want to look at some existing projects to see how they handled these issues.

e.g. http://www.brewtroller.com/

After much searching, I seem to have found a site that has more reasonable actuators. alpscontrol.com -- Now I just need to figure out what will work. Since I've got valves that have positions for multiple outputs, I'm going to need to be very precise in where the actuator takes the valve to. It seems I need a proportional actuator. Not sure what to go with.

I need recommendations on a transformer to take the 240v ac coming into the box and convert it to 9v dc, 1 amp for the arduino.

You should be able to get that wherever they sell electronic parts. i.e. wherever you got your Arduino. Or, you can get usually one at an audio/video store.

BTW - Technically, it's not a simply a "transformer". It's a power supply or power adapter.

I am also needing to power a 120v pump (the march ac-5d-md). I believe the pump needs about 2 amps.

I assume you only have 240 available where you live? It would be better if you can get a pump that works on the available voltage... Otherwise, you need a "step-down transformer". (And, this is simply a "transformer" ;) ) Sometimes electronics-parts suppliers have these. Otherwise, you may need to go to a place that sells electrical supplies (i.e. stuff for wiring houses). You probably won't find one at a "home improvement" store. These are rather large and expensive, but you are working on a large-expensive porject, so maybe it's no big deal...

I'm a little concerned about heat within the box if I've got that much juice flowing through it. (it is a 16x16x8 plastic box)

You shouldn't get much heat inside the box. Power flowing through wires, terminal blocks, switches, or relays shouldn't generate heat. The low-voltage (coil-side) of a relay, or the coil on a solenoid valve will generate a little heat. The real heat is generated where the power is used or consumed (the heaters, motors, pumps, lights...).

Since I've got valves that have positions for multiple outputs, I'm going to need to be very precise in where the actuator takes the valve to.

If this is some sort of rotary valve that's normally manually operated, I'd try to duplicate the function with multiple solenoid valves.

Thanks for the reply. I do have 120v where I live, but I'll be hooking the whole setup to 240v since the heating elements are 240v.

As far as the off the shelf 120v power supply, I don't really want to go with that option since the box will have 240v coming into it. Since I'm going to need to step that down anyway, I figure I might as well try to get it to the 9v DC for the arduino. It seems like a more elegant solution than stepping down to 120v and wiring up the off the shelf power supply. I looked at the tech sheet and it appears the pump will run from 240v, in which case I wouldn't need to step down to 120v at all. I would just need to wire up a different plug.

Since I'm not sure what type of actuator I'll be using, I don't really know what type of step down I would need for those. I've been looking, but have not found something that looks like it will fit the bill. Many of the actuators I've found don't seem to meet the requirement that I have a full 360 degrees to work with. Most are only 1/4 turn. The valves are swageloks (specifically the ss-45xs8 and the ss-45zf8-nd) There does not seem to be extensive documentation on people using the arduino to control valves such as these. Hopefully we can change that.

I do have 120v where I live, but I'll be hooking the whole setup to 240v since the heating elements are 240v.

You don't say where you live, but in my house's breaker panel the 120vac for the lights and outlets is just half of the 240vac feed to the panel. If your valves are not too hard to turn, you probably can use a large servo to turn them.

California. Same setup as you. Ultimately, whatever is used will be a servomechanism, but i'm not going with a hobby servo from radioshack if that is what you were suggesting.

I've been looking at the Belimo actuators. The LU24A is electric and does 360 degree rotation. If I am understanding correctly, there is an angle of rotation limiter that could be used to set the angle of rotation to 90 degrees I could simply advance the actuator or send it back to achieve the desired output of the valves. Is that correct? Anybody used one of these? Seems like a pretty simple way to get around needing feedback on where the valve is. I would just need to incorporate the correct advance or retract cycle for each step.

It appears they are made for air control dampers, but I would imagine it could be converted to work with the swagelok valves (despite violating Belimo's rather archaic instructions that it isn't allowed to be used outside of its specified field of application nor are interfaces not expressly envisaged by Belimo to be made)

The Swagelok (a trademark term, generically referred to as a flareless compression fitting) valves you have linked have very high pressure fittings used with hydraulic power systems and metallic hydraulic tubing. Outside of an industrial setting you'll only find these on construction equipment (perhaps brake lines on cars as well?). Aside from those fittings they appear to have the same construction as a ball valve you would use for a shutoff under a kitchen sink or toilet.

Remember that you don't need feedback on where the valve position is (except knowing where "off" is) but rather you need feedback on the flow going through it. For that you need a flow sensor; simply turning the valve is no guarantee that anything is moving through it and it certainly won't be proportional with a ball valve. For truly precise control it might be cheaper using a DC pump + motor driver + flow sensor combination.

Chagrin,

Thanks for the reply. I used to live in Iowa and had a great time descending upon Dubuque for RAGBRAI a couple years back. Yes, Swagelok valves are pretty intense, but I'm going to be sending liquid at 150+ degrees, so I wanted to go with something that wouldn't involve getting scalded.

I'm not looking to regulate the flow at the swageloks. I'm not sure I need feedback on the flow going through the valve. If the valve is positioned correctly, there will be flow. Since wort is a low viscosity liquid, it will be turbulent flow. If it were high viscosity, and the flow were larimer I could see potential issues with no flow, in which case what you suggested might make sense.

I would like to regulate flow at the ball valve (not a swagelok, but fitted with a NPT to compression fitting) going into the boil kettle. It doesn't need to be "proportional" in a strict sense, it just needs to be adjustable so that I can match the rate at which water is being added from the HLT to the mash tun. Most everything on the setup can be done with the march ac-5d-md pump, which I'll be using to draw wort off the mash tun to the boil kettle. I'll be using a smaller pump (the march 809) to enter the coil in my heat exchanger so that the sparge water is a precise temperature. The problem here is that the water will be going through a 75 foot coil, and that is a pretty significant pressure head to overcome and have good flow. So I'll need to adjust the output of the stronger pump to match the weaker flow of the smaller pump. The only other part in which I anticipate needing to regulate any flow would be the plate chiller out. This seems like it would be pretty simple, as I'm looking to get the wort from the kettle cooled down to pitching temp. A thermocouple and relatively inexpensive solenoid controlled valve should do just fine. If the temp is too high, the valve could close a little. Remember, Since this will have gone through the plate chiller, I'm not worried about getting scalded so swagelok isn't necessary.

With all that said, I'm looking to take the handles off the swageloks and replace them with an actuator. Much of the design is oh hold because I don't know what I need in terms of space in my control box, nor voltage to control this mystery actuator. I know I'm going to be stepping down from 240vac to 9v for the arduino and switching to DC, but I don't know if I will be stepping down to another voltage (say 24) or if that voltage will need to be DC or AC.

Still looking for advice on actuators for the swagelok valves...

In addition, I've started the process of building the box (actually just drilling holes for the receptacles). What I've got are holes for power to the box, the two heating elements, and the 115v standard 3 prong outlet. Holes are tapped for 6-32 screws to hold the receptacles in place. Now I'm at a point where I'm considering the next steps in the build. Since the heating elements are 240VAC, I'm thinking I need 2 SSRs for each element. Is that correct? Also, with 5500w and 3000w heating elements, I was planning on having a common terminal block for each hot wire. Would a 30 amp rated block be sufficient? Then wire from the block to the SSRs? I've also decided on a 2nd box so the high voltage and low voltage components are seperated. What are my options for stepping the power down from 240 to 115 to power the pumps and also from 115 to 9v for the arduino? Pointers would be greatly appreciated!

aurelius: Still looking for advice on actuators for the swagelok valves...

In addition, I've started the process of building the box (actually just drilling holes for the receptacles). What I've got are holes for power to the box, the two heating elements, and the 115v standard 3 prong outlet. Holes are tapped for 6-32 screws to hold the receptacles in place. Now I'm at a point where I'm considering the next steps in the build. Since the heating elements are 240VAC, I'm thinking I need 2 SSRs for each element. Is that correct? Also, with 5500w and 3000w heating elements, I was planning on having a common terminal block for each hot wire. Would a 30 amp rated block be sufficient? Then wire from the block to the SSRs? I've also decided on a 2nd box so the high voltage and low voltage components are seperated. What are my options for stepping the power down from 240 to 115 to power the pumps and also from 115 to 9v for the arduino? Pointers would be greatly appreciated!

Keep in mind if using SSRs for switching high current loads like 5.5kw & 3kw heating elements, you are going to need to use hugh heatsinks for the SSRs. Those maximum amp ratings on SSRs only apply if you can keep the module below it's maximum rated heat dissapation rating, check their datasheets. Considering a typical SSR will 'drop' around 2vac across it's output terminals you do the math to see how much wattage the module must handle. Very large heat sinks will be required at those levels.

At bare minimum id say a 40 amp block
the 5500w is like 23a and the 3000w is 12.5a so 35.5 amps total atleast
Also you only really need one ssr each (rated to 25a and 15a) to switch one leg off, ofcourse this means that the coil is always energized 120v to ground, so don’t touch it unless you turn the supply off
and don’t forget to wire the 5.5k with 10 gauge wire, and the 3.3k with 14 gauge
the supply will have to be wired into your panel with id say 8 gauge on a 40 amp breaker( unless the other stuff adds more
maybe you are best adding a (metal)sub panel with individual breakers for the heaters and other circuits with some space for the ssr (+ heatsink)and have the control circuit in an attached( plastic) box?

I’m using Opto 22’s 45 amp SSRs, along with their heatsinks. I spoke with an engineer at opto and SSRs won’t be working very hard, and the heatsinks will be more than enough. A little overkill, but I figure to go with something that is capable of around double the draw of the each heating element. I’m using 6 AWG wire (8 AWG for the ground) to bring juice to the control box.The receptacle to bring juice to the box can handle 50 amps and is 4 prong (2 hot, 1 ground, 1 neutral) I was planning on wiring each hot leg to it’s own block for distribution with 6 AWG. Since each hot leg is 120 VAC, I should have two separate 120 VAC blocks. And then my tendency to add extra things gets in the way of me visualizing how the layout will work.

From one of the blocks, I wanted use 10 AWG to run power into a transformer/rectifier/smother/regulator to send 9V DC up the conduit to the arduino/display box. Looking on grainger and McMaster Carr, it appears that wiring up another 120VAC plug inside the box and plugging in a simple 2 prong power supply would be much much cheaper. Shame, because it doesn’t really seem like an elegant solution.

I digress.

I’ve been thinking about incorporating some sort of emergency off switch that, if hit, would cut off the power to the heating elements and pumps (but not the arduino). Of course, I was planning on having high and low voltages in separate boxes, and to my knowledge there isn’t an emergency off switch that would run on low voltage DC and be able to send a signal down the 6 feet of conduit to a pretty hefty solid state relay to cut off power to everything but the arduino. Even if I were to use such a switch, would a SSR (even one that could handle, say 50 amps) be reliable enough for this application?

Back on topic now, so I would have two separate 120VAC distribution blocks… Hook up an SSR to one, with the send going to a hot leg of the receptacle for the heating element. Then the other wire feeding the other hot leg of the receptacle would go to the other 120VAC distribution block, right? But then the element is always live, unless I added a second SSR to this hot leg coming from the other terminal block.

I’m curious what you all have to say.