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-   -   My HERMS Build - ready for criticism (http://www.homebrewtalk.com/f51/my-herms-build-ready-criticism-173077/)

Walker 04-13-2010 04:18 PM

My HERMS Build - ready for criticism
This has been under development for a while, but I thought I'd throw it out to the dogs and absorb any criticism.

I am going "half way" here to start. One electric vessel.... the BK. It will serve as my HEX during the mash and then the BK later (sparge water will be temporarily moved from BK to a large pot while I pump wort into the kettle after the mash.) This was a cost savings item... the extra power cable, electronics, heater element, ball valve, etc required for a dedicated HEX doesn't seem worth the scorn of SWMBO right now.

I've got ample room in my control box and amps available to upgrade later and add the dedicated HEX.

My PID does not have a manual mode, but I built a pulse width modulator for a couple of $'s and will use a selector switch to pick whether the PWM or PID is in control of the heating element. When I eventually add the dedicated HEX, the selector switch will be abandoned and the PID will control the HEX while the PWM controls the BK.

The pic does not show the ground wire, but it'll be there in the system. The control box, pump, and element will be grounded.

So... lend me your criticisms now..... I'm ready for it...

edit: all 120V powered items (except the pump receptacle) are mounted on the hinged door of the control box. The 240V stuff is all in the belly of the beast.


There is one thing I think I could/should have done differently, but I'll just be a nuisance if it happens. In that case, I spend another $10 and fix it and the nuisance goes away. But, I'm not going to point it out to anyone. :D

TheAleMaster 04-13-2010 05:22 PM

Just curious as to how you are splitting the black hot - the one that goes to the 25a and 15a mini breakers - as it isn't exceedingly clear from your diagram. :)

Walker 04-13-2010 05:37 PM

Yeah.... sorry. The diagram does not include the power distribution blocks. I'll add them in and re-post the image later.

but, to answer your question, I have two power distribution set-ups.

One (60A rated) sits in the belly of the box. The main cable wires attach to that and then spread out to other items. Hots out of this distro attach to breakers and nothing else. The neutral out of this distro goes to 120V receptacle, one side of the contactor, and to the door for further distribution. Ground out of this distro goes to the receptacles and the chassis (the box itself is 12 gauge steel, except the door which is 14 gauge.)

On the door of the panel (after the 15A breaker that is fed from the main distribution block), there are smaller 30A rated terminal strips that split the hot and neutral out to the switches, PID, PWM, lamp, etc.

Boerderij_Kabouter 04-13-2010 05:40 PM

Are you using a three-way switch between the PID and the PWM? My only concern would be avoiding a situation where both are on and the system is confused.

Looks Kosher to me.

Walker 04-13-2010 05:42 PM

DPDT switch with an "on-on" functionality. It will connect either the 2 PWM relay lines or the 2 PID relay lines to the relay. Not possible to get multiple connections through it.

Brewmoor 04-13-2010 06:05 PM

That is a great idea. I would hate to use the manual mode on a PID. PITA!! Using a dial is so much easier during Boil. I often have to adjust my dial during boil. I would be throwing things if I had to adjust with the tiny buttons on the PID.

I would encourage more people to think about this option if they are running two vessel systems. It just seems like the way to go. Great job.

Walker 04-13-2010 06:14 PM

Thanks. The PWM idea is not mine, but I might have a slightly different circuit for it than most use. I've seen them wired in a "traditional" way where turning the knob adjusts the duty cycle, but also slightly adjusts the frequency of the thing.

Mine is strictly a duty cycle modulator. The frequency is fixed.

Schematic of the PWM:

I've seen people use multiple PIDs in their systems quite frequently on here. It seemed a waste of $ to control the BK with a PID since that PID would only ever be operated in manual mode. The PWM cost about $3 to build... another $1.50 to package up in a plastic box. Much more cost effective than a PID. The PWM gets its DC power source from the guts of an old cell phone charger I had laying around. I just took the plastic casing off, soldered wires to the place where the plug prongs were making contact and dropped it into the plastic box with the small circuit board that the other items were soldered to.

edit: if I had no plans to upgrade later, a PID with manual mode would be all I needed. No separate PWM. but, since I do plan to upgrade later, I have two separate control devices already (for the same price as a PID with manual mode) and now I don't have to build or buy any more control hardware when that day comes around.

Walker 04-13-2010 06:19 PM


I just checked your build thread and saw that you are also using a PWM, but you went the extra mile and etched your circuit board! Nice.

Brewmoor 04-13-2010 06:19 PM

I am using a similar circuit. I used the schematic from this site.


It works fantastic. Like you said. It was cheap too. In my case it cost me nothing. I had the parts laying around. I am sure the parts though only would cost a few dollars.

Edit: If anyone is interested in this circuit. I use expressPCB to make my circuit boards. PM me if you want a copy of the file.

Walker 04-13-2010 06:26 PM

Yeah... that's the "traditional" wiring I was referring to with the PWM. I'm sure it doesn't make a darn bit of difference to have the frequency change a little when you adjust the duty cycle with the knob, but I have some kooky plans in mind for this thing and I wanted the frequency to be fixed regardless of the knob setting. ;)

Nice work, man. (edit: I like the knob you have.... Mine is kind of small, and I'll probably pop it off and put a different one on at some point.)

Parts for the PWM were cheap cheap cheap from mouser.com, but I did have to splurge on a little IC solder board from Radio Shack ($1) because I simply couldn't find one in the mountain of things that mouser sells and got tired of looking.

For power distribution, I bought modular DIN rail stuff from mouser, too. Considerably cheaper than the big bricks I see often, and I can add more outputs to the distribution block for a few cents as the system evolves.

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