DNisich

Recipes 

So, I've been reading about this for a while and think I have a basic understanding. One of you electric wizards out there please correct me if I have this wrong:

Basically, we want to use a 4500W/240V, very low density element and switch it on and off with a solid state relay. The question part comes in as to how to switch the relay. I'd really like to do better than the straight on/off control.

I read about the guy who modified the chase light controller to do it. Sounds good except its a long time time until the holidays when those will be in the stores. Also, I wonder if it would better (or necessary) to have more options than 0/50/75/100%.

I've also read about a couple of systems that use an LM555 and some homegrown circuitry. A little more complex than I would like but will do if I can't figure out something easier.

Lastly, I read through a discussion about using a range burner control (infinite switch) to control the SSR. There seemed to be quite a disagreement about how well this would work. I gotta admit, it really seems that if the range control just pulses on and off for some fixed period of time and varies the on/off ratio to control heat, then it seems pretty logical that using that output through the relay might be just the ticket. I've been scouting Craigslist for a throw away stove to to try to test the idea but, so far, no dice. However, the last post on that thread was that the guy would try it and get back to the group. No further word yet apparently.

In the course of trying to learn more about pulse width modulation, I read some about how modern light dimmers use a similar scheme of varying the time on/off to control a light bulb. This also looks like a pretty good idea. The device is crazy cheap and available in a bunch of places.

How about some of you guys who really know about this stuff chiming in an letting me know what you think of the dimmer switch idea? By far it is the cheapest and easiest to implement. Do you think it would work?

jnortham

Recipes 

Being in the electric process heating industry ( www.durexindustries.com semiconductor processing, chemical processing, plastics processing, aerospace and temperature sensing) I would suggest staying away from monkeying around with the LM555 type timers unless you want to spend more time building and troubleshooting circuitry instead of brewing beer. There are too many readily available, low-cost solutions unless you want to build control circuits for fun (indicative of a sick mind for sure).

Are you trying to modify an exisitng piece of equipment or are you scratch building one?

DNisich

Recipes 

I completely agree about the difficulty and non-necessity of scratch building a 555 based control. Too complicated and I am concerned about what happens if it fails during a brew session.

On the other hand, if a light dimmer with the triac circuitry will work, it will be cheap and, if it should breakdown during a brew session, easy to fix. I think I have figured out a way to test the idea. I will just buy what I think is the correct SSR and wire it up with the dimmer on the control side and single light bulb on the output side. If I can control the brightness of the bulb with the dimmer and through the SSR, then I will be able to control the water heater element also.

This will be a new piece and, hopefully, the start of my all electric brewery.

jnortham

Recipes 

Let me know how it works out. If you find that you need a different wattage element or want to talk about the efficiency of a different element, let me know. I may be able to get something custom built for you at little or likely no charge.