Brown Black Black Black Brown = 1, 0, 0, x 10(exp)0 =100 x 1 = 100 ohms, 1% tolerance
Orange Orange Black Red Brown = 3, 3, 0, x 10 (exp)2 = 3,3,0 x 100 = 33,000 ohms, 1% tolerance.
This code is three figures then a power of ten, then a tolerance. There is supposed to be a bigger space before the tolerance band.

 

Thanks for that.

My multi-meter is definitely not working correctly. Phoned the agent this a.m. and they confirmed your stated steps to clear the REL reading. It was then that I noticed that the auto ranging is not working which explains the jump from a couple of hundred ohms to 4.3k, it is not reading anything in between.

The technician said he would look at it immediately if I took it in. I'm on my way.

 

My original circuit in post #18 is wrong. Here is a mirrored version of the component side to make it easier to tie up with the etch side.

Here is my revised circuit diagram.
The unmarked resistor is 4k7. I don't understand what the bridge rectifier is doing.
EDIT. A thought about the function of the bridge rectifier. I think it may be to discharge the yellow (Timing.) capacitor via the 33K resistors as soon as the triac is conducting.

Les.

 

Yes, the diode bridge and the two 33K resistors clamp/discharge the timing capacitor and undoubtedly improve the function and the lifetime of the controller..
When your multimeter is reading ohms correctly we will be able to suggest a new value of the variable resistor and the added series resistor to reach the setability that is being sought. But I am not convinced that such tight control will be stable as the line voltage changes. For that you need a controller with temperature feedback, and that costs a lot more for anything adequate.

 

Yes, the diode bridge and the two 33K resistors clamp/discharge the timing capacitor and undoubtedly improve the function and the lifetime of the controller..
When your multimeter is reading ohms correctly we will be able to suggest a new value of the variable resistor and the added series resistor to reach the setability that is being sought. But I am not convinced that such tight control will be stable as the line voltage changes. For that you need a controller with temperature feedback, and that costs a lot more for anything adequate.

Thanks,

My multimeter is in ICU and I should have the prognosis on Friday. All functions tested OK bar for all resistance measurements. The technician appeared to be confident that it is repairable.

I will report back when accurate measurements are taken.

As to the accuracy, yes I am aware of the law of diminishing returns when it comes to accuracy. A lack of understanding would have lead to my onerous hysteresis requirements, however I am sure that I can do much better with the input I will get from this thread.

The controller runs my alcohol still which I use to generate a rather fine Gin. Don't do a bad Single Malt either. So better control is always desirable as the process is very power dependent for the production of decent quality.

 

Hmmm, this circuit only seems to trigger on the -ve half cycle... or somethings up with the simulation - just can't see what yet... FIXED


The power v resistance graph is nice and linear..

 

@Andrew Leigh
Which is the 0.14u and 100n capacitor?

 

@Andrew Leigh
Which is the 0.14u and 100n capacitor?

The yellow one was the .14uF

 

The yellow one was the .14uF

i guessed right then...

 

Hmmm, this circuit only seems to trigger on the -ve half cycle... or somethings up with the simulation - just can't see what yet... FIXED

The power v resistance graph is nice and linear..

So although simple the circuit is not to shabby then, good to hear, so I am in with a shout to improve resolution.

Nice to be in the presence of the clever guys

 

linear is not stable... this is a limited simulation not taking into account temperature, noise, mains voltage fluctuations, etc, etc. A preset resistor to give 2700W is not guaranteed to hold it at that output across all those variations. Only a closed loop system with feedback can do that. I did some work with a coffee roaster controlling roaster temperature by varying the opening of a gas valve. It could hold it stable +/- 3degC because there is little lag in a gas fired system; a similar solution with an electric heater is unlikely to be as stable.

 

Have you considered using a PID temperature controller ? This would be a closed loop system that controlled the temperature of the liquid being distilled rather than the power input to the heater. This is a link to one on ebay but there are many more. Jus search for "PID temperature controller".

Les.

 

Notwithstanding the closed loop requirement, if you replace the 4k7 fixed resistor with a 196k 1W resistor (or 180k+15k in series) and use a 50k pot that will give you a range of 2.5kW to 2.9kW with 2.7kW roughly in the centre.

 

Have you considered using a PID temperature controller ? This would be a closed loop system that controlled the temperature of the liquid being distilled rather than the power input to the heater. This is a link to one on ebay but there are many more. Jus search for "PID temperature controller".

Les.

Hi,

I have a PID controller that I started distilling with. PID controllers are not ideal for distilling as they work on temperature. Alcohol is an azeotrope and unlike water does not have a set boiling point, as components in the azeotrope elements are distilled off, the boiling point alters. This means a constant resetting of the set point.

Controlling the still by injecting a fixed wattage is the way to go, it is so much easier, it is actually counter intuitive. Some in the distilling world believe they can control a moving boiling point with a fixed set point. Conventional wisdom is to control the power. There is a great divide between both schools of thought.

 

Notwithstanding the closed loop requirement, if you replace the 4k7 fixed resistor with a 196k 1W resistor (or 180k+15k in series) and use a 50k pot that will give you a range of 2.5kW to 2.9kW with 2.7kW roughly in the centre.

That's awesome,

Is the math's simple Irving? Does not appear to be a normal Ohms Law calculation? Could you please share?

The total wattage is 2.7kW but my problem point is in a different range. On preheat, the temperature is less critical and if it is 2.0 or 2.4kW it makes little difference. The same applies when stabilising the column and settling the still down prior to production. The crux on my particular still is around 1.6kW, at this point 50 Watts makes a large difference and greatly affects the output which one is trying to keep low, at circa 1l per hour.

So my thought process would now be to add the required new components with a switch. So for normal preheats and stabilising mode to use the 4.7k pot then when it gets down to the business end, to switch in your fine tune components. Would this work?

 

There is no 4k7 pot; with the capacitor values you gave the pot must be around 470k - 500k for that circuit to work from approx 100w to 4kW. The 4k7 measured is, I believe, an aberration from your multimeter and when its fixed they will read different.

You could certainly set up some switched presets as you describe. However controlling accurately to 50W could be difficult; too many external variables.

When you say 1.6kW, how are you measuring that? A PID controller maintaining constant and accurate output wattage could be beneficial and relatively easy to set up.

 

There is no 4k7 pot; with the capacitor values you gave the pot must be around 470k - 500k for that circuit to work from approx 100w to 4kW. The 4k7 measured is, I believe, an aberration from your multimeter and when its fixed they will read different.

You could certainly set up some switched presets as you describe. However controlling accurately to 50W could be difficult; too many external variables.

When you say 1.6kW, how are you measuring that? A PID controller maintaining constant and accurate output wattage could be beneficial and relatively easy to set up.

I bought a digital readout with a small current transformer. The readout gives W, W/h, etc. so I rely on that.

I have taken note of the 4.7k pot not being what I measured.

 

Got a link to the digital readout device?

 

Pzem-022 open and close ct 100a ac digital display power monitor meter voltmeter ammeter frequency Sale - Banggood.com

 

I am back,

After 2 and a bit weeks I am informed that my multimeter is not fixable (despite A, V, Hz reading correctly) they tell me that the main IC is blown? How can that be?

Anyways I bought the upgrade to mine as mine was not available. I now have a second meter which can measure all but ohms. This could come in handy.

I can now confirm that the pot is indeed 500k as stated and functioning correctly. The sweep is smooth.

So it is now back to the question as to the resistance now required.

Many thanks for bearing with me.