heating element

[ghostman11]

ERIC your a genius!!! thats a great idea. it would solve alot of problems. i will give it a try on tues (need a trip to get some bits) and let you know how i get on. that deserves a rep cheers mate

 

[ericgibbs]

ERIC your a genius!!! thats a great idea. it would solve alot of problems. i will give it a try on tues (need a trip to get some bits) and let you know how i get on. that deserves a rep cheers mate

hi,
Its important to note that heat dissipation for most passive devices is quoted for a particular voltage and current flowing thru the device and is the Maximum wattage rating,

If you decide to use a 1kWatt electric fire spiral coil element and only power it on for say 10% of the time, then the heat generated/dissipated will be in the order of 100Watts.

I would consider using 'burst' control for the on time of the heater, it still should be switched on at the zero crossing point of the mains cycle.
So that would be when heating is required the element is switched on at the ZCD point and kept on until the required temperature is reached.
When the required temperature is reached, the element will be powered on for a few cycles as required to maintain the required temperature.

This 'burst' method will be easier to build than a PWM system.

If you use a temperature sensing device like the LM35 note the 'long-ish' response curves printed in the datasheet.
If tight temperature control is required chose a more response sensor.

EDIT:
As the heating coil has so little thermal mass the internal temperature of the incubator could easily be changed by changes in the external temperature. I would suggest the heating element heats a aluminium block with a sufficient thermal mass that would reduce the effect of external temperature changes.

 

[ghostman11]

thanks for that eric, the sensors are DS18s20's (4 per incubator) and a sensiron sht71. the control unit i am using at the mo is based around a pic 18f4685.
thermal mass isnt so much a problem as the incubators are very very well insulated and at present take 17 mins to drop by 0.3C, the middle core of the incubators have a heated water jacket (credit to 3v for the origanal idea) and helps maintain a steady tempreture.
this project may seem a bit exstreme for a few incubators but they are used for the more exotic and rare birds we breed particularly the birds we breed for conservation release for people like the royal zooalogical society english heritage and others.
last year we hatched 12 red kite out of 14 eggs and 11 survived wich is a very good hatch rate for theese birds. all but 3 were released this year and apparently are doing well.
the burst method sounds ideal. i like the idea of a 500-1000W heater that we can under power so to speak, i can see many advantages for us.
i may well be asking more questions if thats ok.
once again many thnks for the info.

 

[ericgibbs]

thanks for that eric, the sensors are DS18s20's (4 per incubator) and a sensiron sht71. the control unit i am using at the mo is based around a pic 18f4685.
thermal mass isnt so much a problem as the incubators are very very well insulated and at present take 17 mins to drop by 0.3C, the middle core of the incubators have a heated water jacket (credit to 3v for the origanal idea) and helps maintain a steady tempreture.
this project may seem a bit exstreme for a few incubators but they are used for the more exotic and rare birds we breed particularly the birds we breed for conservation release for people like the royal zooalogical society english heritage and others.
last year we hatched 12 red kite out of 14 eggs and 11 survived wich is a very good hatch rate for theese birds. all but 3 were released this year and apparently are doing well.
the burst method sounds ideal. i like the idea of a 500-1000W heater that we can under power so to speak, i can see many advantages for us.
i may well be asking more questions if thats ok.
once again many thnks for the info.

hi,
Look at this option using a LM35, MOC3081 ZCD, and a TRIAC.

Note the average Power/Wattage over the plot..

EDIT:
A better plot

 

[ghostman11]

my main concerns are accuracy using a lm35 and more so the fact that its far easier to use digital here where a temp can be set and left without having to adjust manualy with a pot.
in our situation its normaly a member of staff that would set up the incubator. we have used comercial setups where you adjust by pot and overal we had problems where distractions etc would mean an incubator wasnt checked often enough dureing the setting up period and incorrect temps were maintained for several hours. the way we do it now is with a menu system where all the operator has to do is select a species from the menu and press a button.
is there anyway i can incorporate the zero crossing detection into the digital system and have that control the on off period of the heater?
i would like to lower operator (error) as much as poss keeping in mind some of the chicks we hatch are worth in excess of £4000 each!

 

[ericgibbs]

my main concerns are accuracy using a lm35 and more so the fact that its far easier to use digital here where a temp can be set and left without having to adjust manualy with a pot.
in our situation its normaly a member of staff that would set up the incubator. we have used comercial setups where you adjust by pot and overal we had problems where distractions etc would mean an incubator wasnt checked often enough dureing the setting up period and incorrect temps were maintained for several hours. the way we do it now is with a menu system where all the operator has to do is select a species from the menu and press a button.
is there anyway i can incorporate the zero crossing detection into the digital system and have that control the on off period of the heater?
i would like to lower operator (error) as much as poss keeping in mind some of the chicks we hatch are worth in excess of £4000 each!

hi.
It should easy enough to use the MOC3081/TRIAC as a ZCD.
Do you have a circuit diagram of the digital system you are proposing.?

See the EDIT on that previous image, it shows the control on the improved plot.

 

[ghostman11]

the other bit of info that might be of use is the fact that the trays are stacked in the incubator and air flow is controled by a front mounted fan array with 4 fans per row per tray. theese are individualy controled using pwm and set sequences. for example if we take a single row the sequence could be fan 1 and 3 on at 30% power for 4 second and fans 2 and 4 off then the fans may switch over to 2 and 4 on at say 45%. the sequence duration and power of the individual fans is based on tempreture and humidity readings per 2 layers of eggs, wich is why each incubator has 4 ds1820's in and 2 sht71's.
i know to many this seems like overkill and a waste of time but is based on 15 years of research i have done part time at the uni. normal hatch rate for a comercial setting is approx 85% of viable eggs, for us we often achieve around 96%, this figure is based on many many thousands of eggs taken over 12 months.
or to put it another way if your hatching battery hen chicks for every viable egg you loes it costs you around 45p so losses are exceptable. for us with alot of the rare stuff we breed and hatch losses can be as high as £7000 per chick so every egg counts .

p.s we also hatch and raise turkeys and geese if anyone wants to order a fresh organic reared one for next year

and before i get moderated this is the first time i have pluged the business lol

 

[ghostman11]

i do have a diagram of the system we currently use but it is being redesigned at present as we are changing the type of incubator we use and because of more recent data. its taking longer than i would like but mainly due to being very very rusty after my long absence from work! i hope to have a working model and diagram by first week of jan. once the changes to the heating system is complete i dont invisage changeing that for a fairly long time. however the other systems will be under development for some time to come.
as soon as i have a reasonable diagram i will post it. the hold up at the mo is because i am considering upgrading the chip we use for some of the controll system.

 

[ericgibbs]

hi,
This image shows only the MOC and Triac.

Connect a PIC output pin to the Control pin on the transistor.

Your PIC software would only have to set the PIC pin high to turn on the heater, the MOC3081 would do the ZCD.

[Note: not suitable for PWM usage]

Do you have a circuit and software you could post or is it confidential.??

 

[ghostman11]

the software and diagrams i have at present arnt of much use as i want to rewrite everything, this is never a fast process as i am a noob! but i will post hopefuly in a couple of days a first draft of the new software with circuit diagram. as for it being confidential i tend not to worry about that as we are so specialised in what we do that we dont have many competetors in this particular field and those we do have we tend to work with anyway.
when you say not suitable for pwm i take it we could still have it switch on and off reasonabley fast say if needed every second or so? or is that too fast?
to me pwm means much higher frequencys.
sorry for the noob type questions but i am a scientist and farmer i am very new to all this electronics

 

[ericgibbs]

the software and diagrams i have at present arnt of much use as i want to rewrite everything, this is never a fast process as i am a noob! but i will post hopefuly in a couple of days a first draft of the new software with circuit diagram. as for it being confidential i tend not to worry about that as we are so specialised in what we do that we dont have many competetors in this particular field and those we do have we tend to work with anyway.
when you say not suitable for pwm i take it we could still have it switch on and off reasonabley fast say if needed every second or so? or is that too fast?
to me pwm means much higher frequencys.
sorry for the noob type questions but i am a scientist and farmer i am very new to all this electronics

hi,
You could switch ON for just one mains cycle if required.!
Thats for 50mSec...

OT: MySon and I have a small farm in RSA, we did buy day old chick for broiler sales, usually had 500 in three, fortnight stages, so about 1500 in total, with a 4th house standing for sterilising for two weeks.

Some of the chicks where only around 36g on delivery, the 45/50g chicks mainly did well, reaching about 1.8/2 kg average for sale.
We couldn't get the profit margins, so after 2 years we scrapped the project.

So we now buy in 50/100's and in house feed for 2 weeks and then free range for about 6 weeks, reaching 2kg avg, its a satisfactory margin.


EDIT:
Farnell have the MOC3081 and BTA06 in stock at 70p and 107p respectively, +VAT

 

[ghostman11]

hi,
You could switch ON for just one mains cycle if required.!
Thats for 50mSec...

OT: MySon and I have a small farm in RSA, we did buy day old chick for broiler sales, usually had 500 in three, fortnight stages, so about 1500 in total, with a 4th house standing for sterilising for two weeks.

Some of the chicks where only around 36g on delivery, the 45/50g chicks mainly did well, reaching about 1.8/2 kg average for sale.
We couldn't get the profit margins, so after 2 years we scrapped the project.

So we now buy in 50/100's and in house feed for 2 weeks and then free range for about 6 weeks, reaching 2kg avg, its a satisfactory margin.


EDIT:
Farnell have the MOC3081 and BTA06 in stock at 70p and 107p respectively, +VAT

profit margins for chickens are very very tight. is one of the reason's we became a hatchery for many types of birds.
looks like your getting good growth rates feeding in house.
at least in RSA you dont have to clear a path to the sheds with a tractor and snow plough
we et better margins on game birds but orders for next year are 80% down. looks like the down turn has even hit the shooting set! we will probaly cull off 60% of our game bird breeding stock in the next few weeks if we dont get orders in. Feed prices have jumped last week by 18%.
although i have to say the budgies have gone bonkers this year and are laying non stop at present!! i have no idea why we still breed them as there isnt much demand as there was and we make a loss on them, but i kind of have a soft spot for them
all our table birds are hatched in walk in incubators that can hold around 30,000 eggs, theese little incubators we make are only for the rare breed low volume stuff. but they probaly account for 70% of our profit.
i hope to have a first draft diagram in a few days so will post it. now is a good time to completely rethink the controllers, the new season dosnt start for us untill mid feb from wich point on we will be running at full capacity. so i have some time to rethink it all

 

[Wp100]

hi,
You could switch ON for just one mains cycle if required.!
Thats for 50mSec...


Farnell have the MOC3081 and BTA06 in stock at 70p and 107p respectively, +VAT

Hi Eric,

Have been following this thread and would appreciate some futher advice on you burst mode plans.

I'm heating a small section of the greenhouse with a 500w heater from a Pic and relay, but this cold snap resulted in the temp dropping too low so I had to up the heater to 1000w, but under more normal times this can over heat a bit more than needed, so can really see the advantage of using the Burst / Triac method.

However wondered what the life of the triac and heater are like when used in the burst mode - is there any big reduction ?

On the practical side, for a 1000w heater, probably 60% use max. what size heatsink would you suggest.
Also could you say what Wattage and Voltage resistors R1, 3 and 4 need to be.

Lastly, I can see the possibilities for the burst mode control loop software ( I'm using assembler), and as someone who actually done a full system, just wondered if you had any good tips on how best to do it.

Many thanks.

 

[ericgibbs]

Hi Eric,

Have been following this thread and would appreciate some futher advice on you burst mode plans.

I'm heating a small section of the greenhouse with a 500w heater from a Pic and relay, but this cold snap resulted in the temp dropping too low so I had to up the heater to 1000w, but under more normal times this can over heat a bit more than needed, so can really see the advantage of using the Burst / Triac method.

However wondered what the life of the triac and heater are like when used in the burst mode - is there any big reduction ?

On the practical side, for a 1000w heater, probably 60% use max. what size heatsink would you suggest.
Also could you say what Wattage and Voltage resistors R1, 3 and 4 need to be.

Lastly, I can see the possibilities for the burst mode control loop software ( I'm using assembler), and as someone who actually done a full system, just wondered if you had any good tips on how best to do it.

Many thanks.

hi,
The life of the element should not be effected, many appliances use this method, including some microwave ovens.

The Triac should last as long as the manufacturers data claims.

Regarding the R1, R3 & R4.
The only voltage that appears across the R1 , R3 series resistors is the forward voltage drop across the triac when its conducting, so I would suggest 0.25W
The same for R4.

I will check the datasheet for the heat sink, to suit a 1kW load.

EDIT:
The Triac dissipates approx 6.5W when running at 100% of the time with a 1kW load.
This Farnell component would be OK for the triac heat sink [ NOTE, the shipping cost compared to the heatsink price!!]
So I would suggest you search for a cheaper option.
The triac comes in two types, insulated and non insulated, so get the heat sink compound/washers etc to suit.

I have assumed that the greenhouse ambient temperature will be around 25C to 30C..??

https://uk.farnell.com/aavid-thermalloy/529702b02500g/heat-sink/dp/1363698

 

[carmusic]

instead of bulding a triac controller just use an ssr on the market that run with 5v signal OPTO 22|240D25|SSR, PANEL MOUNT, 280VAC, 32VDC | Newark.com
, they are cheap and made for that, control of temperature is easy to do since duty can be in seconds like electronics thermostats.

 

[ghostman11]

thanks for the info but at $25 each its hardly the cheap option whn you have 20 odd incubators to upgrade!

 

[ghostman11]

is there by any chance an alternative replacement for the opto isolator with ZCD as the one in the diagram while listed as stocked in farnel is infact USA held stock and farnell want £15 for delivery!!!! seems steep for a £1 part!

 

[ericgibbs]

is there by any chance an alternative replacement for the opto isolator with ZCD as the one in the diagram while listed as stocked in farnel is infact USA held stock and farnell want £15 for delivery!!!! seems steep for a £1 part!

hi Jason,
Look at this from Farnell.
SHARP|PC3SF21YVZBF|OPTOCOUPLER, TRIAC O/P, ZERO CROSS | Farnell United Kingdom

You will find that their search engine is close to useless from the buyers point of view.

It steers you towards the costly items.!!

 

[ghostman11]

thanks eric i get absolutely lost in the farnell site!!

 

[ghostman11]

ive had the same problem with the TRIAC being USA stock so ive ordered STMICROELECTRONICS
BTA06-600BRG hopefully thats ok as a replacement