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I'm a distiller, it's legal where I am (new Zealand) , I want to build a controller for the element in my boiler. Most use ssr and a pot for element control. I want to eliminate the pot and use touch switches, just because I like things different and love tinkering and learning. ...
I have been told that some of my ancestors (or least neighbors) operated 'stills in the hills of West Virginia in the previous century without benefit of government supervision or permission, which was (and still is) a risky business. They didn't use electricity to heat their boilers however.
It is a good thing you like to tinker and learn because I wasn't able to find an inexpensive up/down
power controller operated by push-button switches. Up/down
temperature controllers, yes, some affordable and some not so affordable. So I am thinking a do-it-yourself approach with some off-the-shelf parts is a reasonable approach.
... I really struggle with understanding the electrical side if things though, it's my nemesis lol. Could you point me toward a off the shelf item please?, I have found nothing.
There are a LOT of members here that struggle with understanding the electrical side of things. That's why this community exists: to help each other understand things. If you stick around, and start a project, you can count on at least someone here who has the expertise to help see you through to end.
I don't suppose temperature control is an issue with a boiler running at atmospheric pressure, since the boiling temperature is more or less constant, so push-button up/down power control will be sufficient. The problem is somehow "remembering" the power setting between button pushes, which a potentiometer does nicely. That may be why most off-the-shelf controllers have gone digital, and you should too for this DIY project.
For this sort of thing, I usually turn to
Omega Engineering for the heavy lifting. Why re-invent the wheel when inexpensive wheels abound? Besides the
solid-state relay (SSR), what you need is a pulse-proportional controller that mounts on the SSR and tells it when to conduct and for how long.
Something like this. This spiffy gadget accepts a zero to 30 mA DC current-loop input with a loop compliance voltage of at least 6.4 V DC. It produces time-proportioned pulses to trigger a SSR. It is designed for use in 4 to 20 mA current-loop control systems, but it can also be voltage controlled by just wiring a fixed resistor across the control inputs and applying a variable voltage. So, for 20 mA full-scale input with, say, a 12 V DC supply you need R = V / I = 12 / 0.02 = 600 Ω resistor wired across the control terminals and a variable 0 to 12 V DC control voltage. Then all you need to add is a means to ramp the control voltage up and down with your push-button switches.
The "easiest" way to do that is with either a Microchip PIC with an internal digital-to-analog converter (DAC) or an Arduino UNO which has a built-in 8-bit DAC with 0 to 5 V DC output. Both of these do require some programming, and may not be your cup of tea. There are people here who will help with that.
The Arduino UNO (which is what I would recommend for you) has the advantage of coming pre-assembled and requires just a minimal amount of external circuitry to boost its 0 to 5 V DC DAC output to a 0 to 12 V DC output, while accepting two push-button control inputs. You can power an Arduino from a 9 V wall-wart or battery. To program it, you just connect a cable between the Arduino and a USB port on a personal computer or lap-top, download some free software from the Internet, write the program (called a
sketch in Arduino-speak) on the PC using the free software, and download the program back to the Arduino. The program is stored in non-volatile memory on the Arduino, so once you get it working, the cable and USB connection to a personal computer is unnecessary. If you don't have much (or any) electronics experience, the Arduino approach is the way to go.
A bit less complicated, but requiring some circuit construction is an up/down counter integrated circuit whose binary outputs drive a DAC. Either way you need to determine how much resolution you need, i.e., how much the power changes for each push of a button. I recommend using an 8-bit CMOS counter and a CMOS 8 bit DAC to give you one part in 256 resolution, or roughly 0.4% change in power per button push. Lower resolution makes for a more "jumpy" control and higher resolution means it takes more button pushes to change the power level.
The least complicated, but the poorest performing, is an all-analog means of creating and "storing" an analog control voltage in the range of 0 to 12 V DC. This is very easily done with an integrator circuit (one op-amp, two resistors for up/down, and a capacitor) that charges or discharges a low-leakage capacitor depending on which button you press. Problem is, even with the best components, analog integrator outputs drift up or down over time and eventually the output is either full-on or full-off unless you are paying attention and make push-button corrections for drift. This could be a very steam-punk type of design, with a big analog meter to show the power, appropriately marked in red near the high-end maximum power on the scale. Not really recommended, but it would be fun. You could quickly build it on a breadboard to try it out, and then revert to a digital up/down counter and DAC after you find it too much bother to constantly push the buttons to bring the power back to where you want it. Score one more for the potentiometer approach: set it and forget it.
So, please let us know if you want to make this a project and which approach you want to take.
Hop
. I like the sound of the arduino control, something I've been wanting to learn more about. I think I understand what you've described, I have a couple of ssrs already, so will just need the pulse controller and arduino. I'll get back to you with some.links later in the week, that I hope you can help.me with. Thanks again.mate.
