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What temperature are your haters running at ?
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What temperature are your haters running at ?

You need some serious bad feeling to boil water     smiley

...R
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Hi Guys,

I am using a ladder logic representation for the relay: http://en.wikipedia.org/wiki/Ladder_logic

I've always personally liked ladder logic to understand the circuit - but that may because it's what I'm use to (using it for >30 years).

The temp is ~ 200C so, enough to boil water - but my mass is pretty small so I wouldnt be able to boil a pot of water. essentially, I am heating nichrome wire to seal paper.

Here's the theory of operations:
Checking if Heaters are good - Ardiuno Output 0,1,3 Low and 2 High will Energize only K4. Thus reversing the state of K4 on the diagram. The contacts of K4 shown as open will close and vice versa. No connection from VAC LO to the heaters and the circuit from 5VDC through the heaters will close and complete to Arduino Input. This lets me know if I have a good heater or not

Turning heaters on - Ardiuno Output 2 Low and 0,3,1 High K4 de-energizes and contacts will look as they do on the diagram. K1 and K3 Energize reversing their state as shown on the diagram. Isolating 5VDC and the Arduino input while supplying one side of each heater with VAC HI. K2 Energizes and supplies the other side of the heater with VAC Lo and the Heaters Energize for 500mSec as programmed.

Thanks,
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The OP is using  Ladder Logic circuit representation. I'm not familiar with it either. Never used it.
To test a heater element the only  thing you really need is a variac and a known good heater element for comparison.
Test the known good heater element and plot the current vs voltage. This can be done manually in about 15 to 30 minutes.
Replace known good heater with suspect heater and plot the current vs voltage.
Compare the two.
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200 deg c.

Why do you need to test the heater ?

Nichrome is tough stuff at that temp its not going to burn out.

Is mechanical damage a possibility ?

I think i understand what you are trying to do but i just cannot fathom ladder logic
« Last Edit: September 17, 2014, 01:05:10 pm by Boardburner2 » Logged

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At 500 mSec it gets to the appropriate temp, any longer and it gets a lot hotter.

I had a situation where the heaters were left on for 2 seconds, (due to an inadvertent setting) and they burned up creating an open circuit. The Nichrome melted and curled into two pieces.

From further experiments I know that if the Nichrome is not properly heat sunk at 500mSec it deteriorates quickly.

I am using the heater to seal paper into a tube shape, motors move this tube shape down (index) if for some reason it has failed it will cause an issue further in my process.

Thanks
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So, what is (are) the MISSION OBJECTIVE(s) here ?
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The mission objective is:
Check if heater is functional
If so, close heater jaw and seal (enable) heater, 500mSec
Once done open Jaw and index material
Repeat for variable quantity.
If heater is not functional - report error - do not move anything else in the system.

I have everything working Motors, Jaw open and close detects, GUI etc. - except the check heater, I plan on trying what I've sketched later this week.

Thanks

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Quote
I had a situation where the heaters were left on for 2 seconds,  

Quote
From further experiments I know that if the Nichrome is not properly heat sunk at 500mSec it deteriorates quickly.

What is the normal duty cycle for the  heaters ?

Have you considered using one-shots   ? (555 Timer circuit that outputs set pulse width (ie: 300mS) when triggered with a brief negative pulse) The trigger pulse can be generated from the arduino and the one-shot drives the heater control to ensure it is never on longer than the set pulse width , regardless of sw errors..


« Last Edit: September 17, 2014, 07:16:57 pm by raschemmel » Logged

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Iv not fully thought this through but i cant help thinking that using a diode to half wave rectify the heater supply would simplify things.
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Scrub that, full wave rectify, dont use smoothing.
Use divider resistors  to get voltage below 5 for arduino to sniff.

Tou can test every half cycle or more if you want, you could also use arduino to detect zero crossing and fire an scr.

Nifty way to control the power.

Google on burst fire controller.
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Can't you use a current transformer (CT) to measure the heater current ? Wouldn't that tell you if it was working ?
You can get Voltage Monitors from LEM to measure AC voltages. If you measure voltage and current, can't you calculate the power and tell if the heater is working ?
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If the heaters heat up very quickly why not just test the temperature to prove they are working?

...R
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You would think the OP already thought of that but now that you mention it , it is a question that begs an answer.
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