Help with resistive cartridge heater and variable control circuit

[fastline]

I need to run a cartridge type heater with a variable voltage control. Just looking for opinions as well as a potential supplier for the heater.

Rough specs (not set in stone)
Heater - 120V, 100watt, .25-.500" diam x 1-2" long
Really would like to find a source for these in a smaller bulk orders.

Just not sure how I might make a super simple voltage control for this device. Incoming coming voltage is 120V, out is 120V, so max current would be about 2A with engineered margin.

 

[#12]

If the voltage is AC, you could use a dimmer, commonly sold for use with light bulbs.

 

[4pyros]

Use a 120 volt lamp dimmer providing its AC.

 

[fastline]

Are we talking a common rheostat? those can get down right pricey. i do need to create a small, panel mount barrel knob setup.

 

[#12]

We are talking about, go to the hardware store and pay $5

 

[4pyros]

Are we talking a common rheostat?

NO, A light dimmer for your home will work just fine.

Andy

 

[fastline]

So a triac circuit?

 

[#12]

Yeah. That's what dimmers are made of.

 

[4pyros]

So a triac circuit?

Only if it is AC!!!

 

[Roff]

So a triac circuit?

We don't know where you live, but **broken link removed**

 

[fastline]

i might need 100 of them so price matters. this is ac. i thought some dimmers were still rheostats

 

[#12]

So, what are you building a hundred of after not looking into how dimmers are made for about 40 years?

 

[Roff]

Rheostats waste a lot of power, and probably cost more than a dimmer.
You can probably buy a dimmer for less than you can make one.

 

[Roff]

Google "light dimmer". I found one for $3.48. I also found schematics.
If you can buy a triac, a pot, a PC board, and the other parts, as well as the labor costs, for less than $3.48, you're pretty good.

 

[4pyros]

i thought some dimmers were still rheostats

Not for years but a dimmer does have a rheostat in it.

 

[4pyros]

Do you have more control stuff or is it just the heater and a control. It least a store bought one will be rated and fit in a standerd box.

 

[Reloadron]

As to the heaters give this a read. Since you mention a few diameters I think you will find a 3/8" diameter heater that will meet your requirements as to diameter and length. You can look through the cartridge heaters found here.

I only used Omega as an example. These things are pretty standard and truth be known they are only made in the US by a few companies but marketed with everyone's name on them. I believe Watlow manufactures for Omega but not sure. Anyway prices vary so shop wisely and once you decide based on heater specifications make sure you are correct. Then shop and buy.

As to control? Buy a light dimmer for a load as light as 100 watts as was well covered. Incidentally a cartridge heater rated for 120 volts 100 watts doesn't care if it sees 120 VAC or 120 VDC volts. They are purely resistive devices. That assumes 120 VAC RMS.

Since you don't mention actual temperature control I assume it isn't required for your application.

Oh yeah, cartridge heater are generally undersized as to diameter so a standard drill bit can drill the holes. The clearance will be fine.

<EDIT> Chromalox is another big name in heater elements including cartridge heaters. They can be found here. </EDIT>

Ron

 

[fastline]

Thanks for the replies guys. yes, this circuit is one of a few that will have to be put on a PCB. I have little experience with triacs and mostly work with DC stuff so this will be a bit new to me. There is also a fan control and device protection circuit that will have to integrated.

Yeah, it is always frustrating that you can literally go buy a complete device for less than you can get the parts for. Go look at a radio controlled gadget at Wal Mart in the kids isle. I guess I was just hoping there would be a stupid simple way to regulate the voltage to this device but sounds like not...

 

[4pyros]

I guess I was just hoping there would be a stupid simple way to regulate the voltage to this device but sounds like not...

Nope you need a triac dimmer circuit, thare are thousnds of them on the web. How will you control this manually or with a controler of some kind? Andy

 

[fastline]

This will just be manual control with a pot. I was poking around for circuit designs. Still trying to understand why the diac is a requirement. obviously because of the non-lighting load, a little flicker here would not be any concern at all. My goal is to use the least amount of parts possible to achieve my goal. there would be two of these circuits back to back, one for the resistor, and one for a small fan. I would probably just have the PCBs made but sure would be great to find a premade PCB though. We have always resorted to mfgr for them. I know these are really simple circuits so just hoping I guess...