Incubator Thermostat

[chrismahon]

We have a spanish semi-automatic incubator from Ascott which, because we used it without a surge protector socket, had the thermostat circuitry melt down. It's a good solid unit and has had many successful hatches. We replaced it with a Covatuttu24 (€170 -ouch!), another good unit, until I could examine what could be salvaged. So the motor and heater work fine, it's just the thermostat that's beyond repair.

There have been many home-made incubators in the past on the forum. But the thermostats they used had a 2 degree switching range, which I think is far too wide. I've seen wafer thermostats on American sites, but fitting one to this unit would be difficult. There are now cheap Chinese solid state units but they have the same 2 degree switching range.

Has anyone found anything better or will 2 degrees be OK, but with reduced hatching rates perhaps?

 

[chrismahon]

So more research and I'm getting nowhere. The professional incubators have a switching differential of 0.1 degrees. I don't actually know what the home incubators switch at, but the heater lights are on and off quite quickly so it must be in the same range. the units designed for hatching are:-
A mechanical wafer (diaphragm) stat from USA has a 110v microswitch, so may not take 240v.
A digital electronic from USA which has a differential of 0.2 degrees F. but is also a 110v unit.
The others considered:-
Maplin electronics unit is only 12V and no stated differential.
Reptile tank heater unit, which I know from previous discussions I have read is over +-1 degree, but it is 240v.
STC1000 digital thermostat with probe (Chinese). Lots of fancy blurb on eBay, all of which misses the essential point. I have sent an enquiry but don't hold out much hope. I may have to buy one and test it, as I have an infa-red thermometer with a measurement accuracy of 0.1 degrees.

This 'incubator thermostat' question has been asked on other forums in previous years (Google search) and the general advice seems to be to buy another incubator!

The Brinsea web site has replacement thermostat assemblies for all their models. Expensive, but perhaps one can be made to fit? Still far cheaper than a new incubator.

 

[MalcolmP]

Hi Chris, sorry to read of your surge prob.
As with all Brinsea stuff it is expensive but it is good !
I have used their electronic thermostat to replace the mechanical (ether capsule? wide differential) thermostat in one of my very old Brinsea Electroturn80
The best thing about it is that it is a 'proprtional' controller with an electronic (semiconductor) switch controlling the heater. A lot of other types, Maplin included when I last looked a few years ago, use a mechanical relay to switch the heater which are prone to failure unless a professional or mil. spec. is sourced !

The nice thing about the proportional types ( compared to switching/ bang-bang types) is that the differential (aka hysteresis ) is small. Pulses are sent to the heater, if temp. rises the pulses become shorter, if temp falls the pulses get longer, so the controller is 'on the job' continuously.

If you do go for a cheaper switching type : one way of reducing the effect of the wider differential is to place the thermostat sensor close to the heater * (even maybe include a part shield round them both), the heater-stat combo will then cycle quickly between limits while the thermal capacity of the rest of the incubator volume will keep it nearer the average.

Does the current Maplin unit cover the range we want ? Used to be that a mod. was needed to lift the comparator up to 37C ( an extra resistor in the divider chain)

* I dont know your incubator so dont know if that is possible, these are all just a few random thoughts for you, typed quickly before I rush out into the garden to enjoy this strange new phenomenon called summer which has just hit the UK

 

[chrismahon]

Hi Malcolm. And I thought French was difficult to understand. I've understood the proportional heating-something I would not have thought about. I guess I buy whichever controller they have that fits inside my casing. I must have a temperature probe on a lead version because there is no chance of theirs being in the same place as mine. Tried for a replacement assembly from Ascott, but the one they do won't fit the older models and ours is 7 years now.

Electricity in rural France is a bit hit-and-miss. The voltage is unstable and ours is running at 240V usually, to ensure 220v further down the lines I suppose. But it sometimes drops to 220V. Being 3 phase complicates things as well. Obviously you get spikes between power cuts and that's what blew the control unit, something I overlooked when setting up the incubator. we had so many power cuts we bought an alarm unit so I could get up to set up the inverter. 12 hour cuts are not unusual so the freezer needs to be full of ice bottles.

Enjoy the Summer Malcolm. Forecast here is sun for over a week with the temperature rising to 35 degrees (in the shade, our greenhouse went over the 50 degree scale -drying wood for winter) but will be 15 degrees higher in the sun. Can't say I enjoy it much as it slows my work rate rather a lot -in fact I grind to a halt and head for the trees.

 

[MalcolmP]

"a temperature probe on a lead version"

That is what I chose, so I have mounted the electronics on the outside of the 'bator, the probe is then inserted through the hole where the power lead used to be. A new power lead and a feed from the electronics to the heater also go thro' that same hole, it was a tight squeeze but saved me drilling a new hole in the fibrglass wall.
( I dont like fibreglass ! )
This way I have easy access to the temperature adjust and good view of the little red led showing the state of the thingy.

Just wondering aloud : with the electric being that unpredictable would a 12v system round the Maplin ( or similar) 'stat be worth exploring ? You would need to sort a 12v heater, but then the whole lot could be run from car/lorry battery. With a mains charger for when the mains is there and a long lead out to your car, motorcycle, or other petrol powered 12v alternator (or dynamo) for when it isnt.
The mains charger with the battery hanging on its output would also isolate you from spikes, especially if you put a capacitor across the 12v.
Hmmm, I'll go away and scratch my head and wonder what the typical consumption of an incubator is. Ie. could a car battery without petrol assist sustain it for 12 hrs. Probably, if it was well insulated and airflow kept to a minimum.

 

[chrismahon]

Consumption is about 80W on ours and it is as well insulated as possible without blocking the airflow. We have a device to measure appliance power consumption because the meter over-read by 30% when we got here and we have had to pay €60 for a new meter- that's the system here. So at 12V that's 7 Amperes roughly and with a 100 Ah battery draining to 60% gives you 6 hours Malcolm. When we went out we ran the incubator off a battery through an inverter. Danger was if there was a power cut when we got back the battery was then discharged -at one stage I had to leave my van running outside to get power to the incubator.

 

[MalcolmP]

at one stage I had to leave my van running outside to get power to the incubator.

That's hatching 'in extremis' !
Perhaps the ancients had it right with their paraffin heated 'bators !!
Mind u, paraffin is a bit rare in rural uk these days

>"Consumption is about 80W"
Gosh I am surprised, I would not have guessed that much
>"So at 12V that's 7 Amperes roughly"
plus the conversion losses in the inverter, or did you factor that into the 80w ?
So, yes, no wonder the battery got a bit stressed.

If you did go for a 12v 'stat and heater system that would eliminate the inverter losses.

Hmmm, just looked at the Maplin site, http://www.maplin.co.uk/thermostat-kit-31698 ,RR51F is that the one you looked at ?
The relay is only rated at 24v (although a discussion in their forum is talking about it (Velleman) having a 125v relay), so a bit of a fiddle with another relay to handle the existing mains heater.
Temp.range up to "about 30C" so, as I said previously mods needed there.
And the worst bit - "out of stock, expected 30days" (maybe !)

 

[MalcolmP]

a bit more googling and :
http://www.esr.co.uk/velleman/mk138.htm
have it (same picture as on the Maplin site) (£4.55 instead of £5.99 but I didnt look into p&p ) and they also list the mods needed (quote)
"To make it suitable for use as an egg incubator thermostat (37.5º) with a hysteresis of approximately ±0.4º."
My underline.
They have a ready built version for £7.95 but from the description it seems not to include the mods (maybe worth enquiring about a special build ?)

Cheap enough,, leaves a bit spare for some Jaffa Cakes over the Brinsea one

 

[chrismahon]

Jaffa Cakes Malcolm -what the hell are they?? I knew this electronics stuff was complicated. Je pence I'll get one of the Brinsea units as they have expended the brain power so they deserve the extra.

 

[MalcolmP]

get one of the Brinsea units

Good choice I think, least messing about. I've had mine in my No1 machine for a while now, many hatches no probs. holds temp. to 0.1C on medical thermometers.

I do fancy the el-cheapo Maplin/Vellman thing tho', think I might have a play with it substituting the relay with a MOSFET ( or the driver transistor and relay with a Darlington pair) and turning my No2 machine into a 12v setup.

Good luck,
or, je pence, bonne chance.