Trying to design a super efficiant heater

For saftey you should think about using a one time thermal fuse somewhere in the circuit, just to cut the whole thing off if some upper limit is reached. All laser printers I've ever taken apart have a thermal cutoff on them, just in case. They're designed to heat up FAST which means they can actually heat MASSIVLY higher if they weren't limited somehow. A typical laser printer fuser module could easily catch the printer on fire during a fault if no emergency thermal cuttof was available.

Given that you need a rather fine range of response you may be better off with high insulation values and a smaller wattage but still sufficient heater system.
Its response time will be slower but it will eliminate over shoot as a trade off. If the heated parts have a fair thermal mass that will help stabilize the temperature drift associated with the heater cycling on and off as well.

Making an accurate thermostat to maintain a close temperature range will likely be more of a challenge than the the rest of the design.

is it possible to install a pot inline with the resistors to limit and increase the ohms allowing me to set the continuous temp output to 99.5 degrees?

By the way thanks for the input Dimwatt. Here are the links for the bators he's talking about if your interested.
Dickey Incubators
**broken link removed**

Both have all 120v equipment. They are built with hvac parts. Like inline duct fans, thermostats, and grossly over rated turner motors. I have seen the dickey run over 500 watts. I can't tell you about a sportsman's. I've never touch one. All i know is that dickey copied the sportsman but made is cheaper. Basically what i'm doing but keeping it the same price but making it better.

cbiblis said:

is it possible to install a pot inline with the resistors to limit and increase the ohms allowing me to set the continuous temp output to 99.5 degrees?

Click to expand...

It will have to have a huge power rating.

If you use a solid state switch (e.g. a triac) to drive the heater you can use a high continuous-power heater but dynamically adjust the heat output to give the heating response you want.

dougy83 said:

It will have to have a huge power rating.

If you use a solid state switch (e.g. a triac) to drive the heater you can use a high continuous-power heater but dynamically adjust the heat output to give the heating response you want.

Click to expand...

in order for me to understand you better could up whip up a draft of the circuit. or just tell me the components and what configuration?

To make it even more simple could i use a dimmer switch to regulate the output to the heater?

Yeah, a dimmer will let you adjust the power output of the heater.

That's what I was kinda getting at with the solid-state switch, except that you would dynamically adjust the output to control the temperature.

i will try a dimmer on the nichrome wire and see what i get. Thanks

You can adjust the power to the heater with a dimmer...but...there's no temperature feedback. So, any changes in line voltage will change the temperature. There's no compensation for heat loss due to opening the cabinet, so it will take a lot of time to return to the desired temp.

Ken

What i'm pictureing is this:
I run a 60ohm 120v nichrome wire. I will install a dimmer switch inline for constant run. I could set it to hold a constant temp of 99.5 degrees. Then with the thermostat i will set to 98.5 degrees and run wires to bypass the dimmer switch. There by eliminating a on and off setup to a high and low setup.
Does this sound good?

How about an all in one device tempurature control device.

These microprocessor based all in one solid state relays are specifically designed for applications such as what you are doing. Just add a thermocouple, a potentiometer, and a basic power supply and your good to go.

They cost 110 dollars. I can build one for less that 10 dollars. Are you confident with the out come of the design i propose?

Just one thing.

Efficient, accurate, precise... are words that do not combine with the word "cheap".

I thought you where the one arguing that price was no object when dealing with eggophiles.

I would like to see you build the same device for $10 as well!
Post a honest parts list and schematics and prove it!

tcmtech said:

I thought you where the one arguing that price was no object when dealing with eggophiles.

I would like to see you build the same device for $10 as well!
Post a honest parts list and schematics and prove it!

Click to expand...

That's until they see the price

$110 is cheap for a working solution vs some cobbled together $10 prototype.

Well you know how stuff is. If it looks very impressive and costs a lot it must work well too. Its not like a custom made high dollar chicken hatcher is going to have a few 10 watt radio shack resistors and a light dimmer for the heating system and controls is it? I mean after all that what some mutt chicken farmer would have on his cardboard box!

After all isn't keeping those $100 a piece eggs in perfect harmony with the universe what its all about? Its not the profit to be made behind the product that matters!

Well first off i don't plan on using a dimmer switch in the final design, i'll design and build a solid state relay with triac on the system pcb, i still have plenty of room. Even though it would probably be the best option to use that component This is a competitive market. I could offer it as an upgrade. And i won't be using the resistors like they are in the picture. i cobbled that together to test the theory. As a matter of fact if i build this system then all i will have in the cabinet for heating would be the coil nichrome wire. All of the components will be on one board and cased in the project box out of touch from curious fingers of the customers.

tcmtech said:

I thought you where the one arguing that price was no object when dealing with eggophiles.

I would like to see you build the same device for $10 as well!
Post a honest parts list and schematics and prove it!

Click to expand...

Take a look around your shop. What is the most expensive item inyour shop. Is there a better one available on the market. If so, why dont you own one. Does the answer have to do with price?

Nowhere have I seen anybody suggest that price was no object. there is a precieved price threshold for most any object you can purchase. "Oh, that cost to much, this model is cheaper and I can make do with that instead of the better more higher priced model." What Cbibilis seems to be trying to do is produce a better incubator than is currently on the market, and he is wanting to keep the price competitive with what is already available. Been there, done that and know what he is up against. What I cant understand is someone that seems to be posting in this thread that doesnt have a clue about what Cbiblis is doing or why, but only seems to post to make a racket. I imagine Cbibilis as someone that is trying to learn how to do much of his project himself and is asking for advise from other more knowledgeable about the processes involved than he is. A few have helped and others have just made crude remarks. He will undoubtably make many mistakes, but based on the projects he has already completed, he seems to be learning from his mistakes.

I dont know squat about electronics and am just hanging out here on this forum reading and trying to pickup a few things myself. I dont have any real interest in electronics but came to this forum looking for help on a very similar project. (the real reason I have been following this thread). My thoughts are that if you cant help someone, then why bother commenting in the first place.

Cbiblis, that's a very impressive cabinet! You need a nice controller to go with it.

I recently created a nice open-source temperature controller, complete with LCD that displays the actual temperature and the setpoint temp. It was designed to use the very cheap PIC 12F675, and my little cheap Shift1 PCBs. And 2 buttons to turn the temp setpoint up or down.

Have a look at controller here;
SH1_Temp2 Temperature Controller

You don't need much more than a transistor and relay to operate your heater element, and the temperature sensor I chose was LM335 again because its a cheap and fairly accurate sensor. This controller is fully designed, tested and proven, it's perfect for low temp dryers and incubators and you can assemble them very quicky as there is only a few parts on the PCB.

If you are intertested in using this controller I can sell you a small quantity of the little Shift1 PCBs very cheap and you can source relays and LCDs at your end.