honey warmer thermostat which one?

[herefordshirehoney]

I've ironed it to down to th**nes kit or ecostat's. Which one would you go for out of the two?

Is one more suited to attached to the back of kingspan? It will be a temporary box ie. ie. it will complase when flat.

 

[Hachi]

Digital temp controller via China £10
Temp probe via China £1
Tube heater from A**z** £14

Kingspan - yet to be bought but will fold down for storage.

I got help from some good people on here to do it all I need now is the honey.

 

[herefordshirehoney]

Which ones did u get from eBay then it's all too complex with choices hence why I was thinking of easy route.

 

[barratt_sab]

I used one like this:

http://www.ebay.co.uk/itm/Digital-T...ial_Automation_Control_ET&hash=item5af18e631b

(the vendor is nothing to do with me, and if you search for "temperature controller" you'll get loads of sellers of this device - just look for the orange cabinet catches on the side - BUT check the supply voltage is what you want (I wanted mains supply and load))


to make something that looked like this:

http://www.beekeepingforum.co.uk/showthread.php?p=247721#post247721

which now has proper box.

The controllers have screw block connectors in the back for a mains feed to the controller, mains feed to the relay and switched mains from the relay. There is another pair of screw block connectors for the temperature probe.

I connected the switched mains from the relay to a trailing socket, so I could use it to power different loads. So far I have used with with a vivarium heater (low power, low temperature heating wire) to warm supers and cider. You could use it to switch a light bulb to heat a warming cabinet. I have also used it to control an incubator for chicks. Obviously, you need to make sure that the load is not too high for the relay, or else you need to uprate the relay.

 

[barratt_sab]

and if you search

http://www.homebrewtalk.com

for "STC-1000" (the model number of this device) you'll see discussion about how to hook it up to various loads.

 

[Hachi]

I used this one:

http://www.ebay.co.uk/itm/PID-FC-DI...ial_Automation_Control_ET&hash=item5655a055db

Derekm+ will tell you whether you need a 'M' or 'K'

 

[derekm]

I used this one:

http://www.ebay.co.uk/itm/PID-FC-DI...ial_Automation_Control_ET&hash=item5655a055db

Derekm+ will tell you whether you need a 'M' or 'K'

there are two variants:On one the output is a relay contact, the other that is a voltage for a solid state relay (SSR).
Both use type K thermocouples.
Make sure the model number is
If buying this make , the model number needs to be REX-C100FK02-M-AN

 

[herefordshirehoney]

The one barratt_sab posted looks easier easier to operate would this function ok? Still not sure what heating cable to get tho or tube heater as there are too many choices. Its 50mm celetex equiv of kingspan that should hold 4x 30lb buckets in 60cm x 80cm celetex box. 25w is probably too low for that.... the ecostat is 100w I believe.

 

[itma]

The one barratt_sab posted looks easier easier to operate would this function ok? Still not sure what heating cable to get tho or tube heater as there are too many choices. Its 50mm celetex equiv of kingspan that should hold 4x 30lb buckets in 60cm x 80cm celetex box. 25w is probably too low for that.... the ecostat is 100w I believe.

A "PID" controller offers much better temperature control - after you have set it up properly (and here I'm talking about the parameters you enter or tweak after 'autotuning').
A PID plus a solid state relay can provide awesome control. A bit like a computer controlled dimmer switch.
But its not needed for this job, and unlikely to be simple to setup well.

A simple "thermostat" (as linked by barratt_sab) doesn't need proportionality adjustment. It turns the heater full on or full off. Generally you can set a target temperature and an 'allowed' range - like only turn on the heater when the temperature falls more than your allowance below target. Something like 1 degree C should work fine. (You don't want if switching too nervously.)
That one has a relay (for your heater) included inside. The relay seems to be able to handle 10 amps (so 2200 watts - way more than your likely heaters).

Because you are controlling the temperature with the thermostat, as long as the heater is big enough (providing enough heat) without being absurdly too much, the size of the heater isn't critical.

I'd suggest that you wire up your controller's output relay connectors to a socket - so that you can switch whatever 'heater' you choose to simply "plug in".
Consider the 'output' terminals to be the terminals on a switch.

1/ If you don't know what you are doing, get hands-on help.
2/ Run your homebrew system through an RCD safety plug or socket (£5 well spent on life insurance).
3/ And include a small fan in your box to even out the temperature ... and thus make sure that what the sensor is experiencing is typical of the whole box. A low-voltage fan from a scrap computer plus an old (transformer) fat plug from a broken gadget should cost almost nothing - and be fairly safe. Just make sure the voltage is appropriate!

 

[herefordshirehoney]

Great thanks thinking of giving this a go now. The final thing is what to use as heater.

Would this work:

http://www.ebay.co.uk/itm/Electric-..._Hearing_Cooling_Air&var=&hash=item53f3677720

single 60watt.

I'll probably attached the heater permanent to the celex roof, so the plug idea would work well.

 

[derekm]

A "PID" controller offers much better temperature control - after you have set it up properly (and here I'm talking about the parameters you enter or tweak after 'autotuning').
A PID plus a solid state relay can provide awesome control. A bit like a computer controlled dimmer switch.
But its not needed for this job, and unlikely to be simple to setup well.
e!

They all have auto tune these days... wire it in and it just goes no fiddling required.
A honey warmer under 500W can just use the relay version no need for a SSR.
PIDs are now cheaper than thermostats... We use one on a seed germinator the same one to warm up microscope slide stain.

how I remember the happy hours at Linwood refuse disposal incinerator trying to get an analogue PID controller to control the gas temperture exiting the wet scrubber before the electrostatic precipatator. That was back in the 1970s... All that twiddling not needed any more we have clever digital ones now..

 

[itma]

My suggestion would be to put the heater low down (not high up), with the temperature probe something like halfway up, and NOT directly above it ... because heat rises!

Really, after you have made your box, you should try it out with a lightbulb or two - without necessarily any 'payload'. Just so you can see how good the insulation is. With a 60 watt lightbulb, on constantly, what maximum temperature does your box reach? (Note also what the room temperature was - because its really the difference between in and out that your lightbulb creates that matters.)
Use the computer fan to circulate air and even out the temperature when making this test.

If 40 watts is enough to reach the temperature you want, then I'd think that a 100 watt heater would be enough for warming a load of honey, to get it up to that temperature - at which point the heater would be on for 40% of the time ...)
I'd avoid putting any "large mass" heaters directly under the honey, because that mass is very likely to give a big initial temperature overshoot close to the heater. Yes, that's exactly the sort of thing that you'd expect a well-tuned PID to avoid ...

 

[Little John]

A "PID" controller offers much better temperature control - after you have set it up properly (and here I'm talking about the parameters you enter or tweak after 'autotuning').
A PID plus a solid state relay can provide awesome control. A bit like a computer controlled dimmer switch.
But its not needed for this job, and unlikely to be simple to setup well.

Thank goodness someone has posted some sense ...

You only need PID control when you're trying to control a system where 'something' (that which you're measuring) is constantly changing.
The algorithm was established during the early days of marine autopilot design, as a result of watching an experienced helmsman constantly countering the ship's yawing motion by anticipation.

But this is a honey-warming cabinet, where 1 or 2 degrees either side of set-point isn't going to make an arse of difference.

Suggest you source a simple on/off controller, and keep the hysteresis (if it's adjustable) to half a degree of so. That's plenty good enough for this job. And no PID parameters to set up - if you're ever seen the crazy antics which a mal-adjusted PID controller can produce, then you know exactly what I mean ! Calling it 'unstable' doesn't do that fiasco justice.

LJ

 

[VEG]

Wish I knew what the hell you were talking about lol thats why I bought the egg incubator plug it in turn it on no electrickery experience needed lol

 

[itma]

They all have auto tune these days... wire it in and it just goes no fiddling required.
...
how I remember the happy hours at Linwood refuse disposal incinerator trying to get an analogue PID controller to control the gas temperture exiting the wet scrubber before the electrostatic precipatator. That was back in the 1970s... All that twiddling not needed any more we have clever digital ones now..

The problem is that the tuning parameters will depend on the thermal mass involved - specifically the amount of honey loaded.
Because autotuning involves overheating and then monitoring the cooling rate, you might not want to autotune with a load of valuable honey.
I had to tweak the parameters after autotuning to get stable control on my sous vide cooking waterbath - but admittedly that is awkward as equilibrium only requires about 5% 'on time'. And the system has a long delay. But it works.

And my intro to "3-term controllers" was also in the 70's. But for flow control (tank levels and pump speeds rather than temperature) round a vast hydrometallurgical plant. They rarely worked, and were kept as a black art by the Instrumentation Engineers (who couldn't make them work either.)

 

[derekm]

My suggestion would be to put the heater low down (not high up), with the temperature probe something like halfway up, and NOT directly above it ... because heat rises!

Really, after you have made your box, you should try it out with a lightbulb or two - without necessarily any 'payload'. Just so you can see how good the insulation is. With a 60 watt lightbulb, on constantly, what maximum temperature does your box reach? (Note also what the room temperature was - because its really the difference between in and out that your lightbulb creates that matters.)
Use the computer fan to circulate air and even out the temperature when making this test.

If 40 watts is enough to reach the temperature you want, then I'd think that a 100 watt heater would be enough for warming a load of honey, to get it up to that temperature - at which point the heater would be on for 40% of the time ...)
I'd avoid putting any "large mass" heaters directly under the honey, because that mass is very likely to give a big initial temperature overshoot close to the heater. Yes, that's exactly the sort of thing that you'd expect a well-tuned PID to avoid ...

If your honey warmer has the crossectional area of a national hive... and you insulated it with 50mm kingspan, Then you will only need about 20w to keep the top part of it 40C above ambient. The extra heater power is needed to k get it there. If you have another 40w on top that should get 20kg of honey to 40c above abient in about 9 hours using a specific heat of honey of 2100 Kj/kg/k

 

[itma]

...
You only need PID control when you're trying to control a system where 'something' (that which you're measuring) is constantly changing.
...

In this case that would be the temperature of the honey payload and thus the rate of heat flow into it.
A PID should get the honey up to temperature faster with less extreme overshoot than a 'bang-bang' thermostat.
Ideally, in theory.

But I'm not disagreeing.
Its not needed here.
Particularly for someone unfamiliar with the concepts, it is best avoided.

 

[barratt_sab]

Generally you can set a target temperature and an 'allowed' range - like only turn on the heater when the temperature falls more than your allowance below target. Something like 1 degree C should work fine. (You don't want if switching too nervously.)

Yup - this controller allows you to set a threshhold range below a target temperature - only in single digit degrees C (e.g. 1, 2, 3, or 4 deg C).

That one has a relay (for your heater) included inside. The relay seems to be able to handle 10 amps (so 2200 watts - way more than your likely heaters).

Yes, that's the rating on mine - I worried about the PCB tracks leading to the relay, so I've put a 3amp fuse in the plug that powers both the controller and the load (and not managed to blow it yet).

I'd suggest that you wire up your controller's output relay connectors to a socket - so that you can switch whatever 'heater' you choose to simply "plug in".

Yup - that's my trailing socket (it only took me about 4 weeks to think of that one...) - as you say, you can switch between whatever loads you want. I put the socket on when the thermostat in the chick incubater went on the blink, so I just turned the incubator up to its hottest setting, put the probe in with the eggs and plugged it into the socket.

1/ If you don't know what you are doing, get hands-on help.
2/ Run your homebrew system through an RCD safety plug or socket (£5 well spent on life insurance).

Definitely

 

[derekm]

The problem is that the tuning parameters will depend on the thermal mass involved - specifically the amount of honey loaded.
Because autotuning involves overheating and then monitoring the cooling rate, you might not want to autotune with a load of valuable honey.
I had to tweak the parameters after autotuning to get stable control on my sous vide cooking waterbath - but admittedly that is awkward as equilibrium only requires about 5% 'on time'. And the system has a long delay. But it works.

And my intro to "3-term controllers" was also in the 70's. But for flow control (tank levels and pump speeds rather than temperature) round a vast hydrometallurgical plant. They rarely worked, and were kept as a black art by the Instrumentation Engineers (who couldn't make them work either.)

try it out with 1/2 the weight of water to simulate the thermal mass.

 

[Little John]

In this case that would be the temperature of the honey payload and thus the rate of heat flow into it.

Well ... yeah ... but not constantly changing - like in an autopilot, or in a steel-rolling mill where quenching might takes place intermittently, or in a high-speed paper web (think newspaper printing machines), where sudden step changes in error - and in the rate of change in error- can be real buggers to control.

But I think we essentially agree - although is achieving set-point rapidly without overshoot really a priority here ?

In my experience, the main problem with the use of PID controllers is not with the controllers themselves, but rather with the people who want to use them - for there is so often an expectation that they can work miracles.
Even in an inherently unstable system, it is so often expected that just hooking-up an expensive wizzo device (at least they used to be expensive - my guess is that the Eurotherm 810's that I used to use still are ...) will instantly be able to control anything - and of course, that's just so much cobblers.

The really important thing which is so often overlooked in applications such as this, is to keep the thermal transfer medium well stirred - just the simple investment in a small fan to keep the warm air circulating will improve temperature control significantly.

LJ