Check my wiring scheme please

[Blue]

Would you folk mind having a look at my wiring of this control box. I am very inexperienced indeed in this field, my speciality is antique clock movements. I am building a tool to blue steel parts under heat. Below are pics of the planned tool, a pic of my progress in wiring the control box components, and also a pic of the wiring diagram that came with the PID temp controller.
Many thanks in advance

 

[(*steve*)]

IMPORTANT: Connect the protective braid from the thermocouple to protective ground (earth), and also cover it with heatshrink etc. in the case so it doesn't short out to anything.

For safety, if you can obtain/make a plastic cover for the SSR and the back of the PID controller that would be good too.

For initial testing, I'd replace your heater with a low wattage bulb.

The first test is that the LED on the SSR is illuminated when you think the heater should be turned on, and that the bulb lights. Both should be off otherwise.

Using the blue/brown wires for the low voltage wiring is confusing, but they seem to go to the correct places as far as I can tell.

 

[Blue]

IMPORTANT: Connect the protective braid from the thermocouple to protective ground (earth), and also cover it with heatshrink etc. in the case so it doesn't short out to anything.

Thank you for your feedback steve, much appreciated. Would connecting it to the heatsink under the SSR be appropriate? Any ideas as to how to do this with unravelling the protective braid?
It will be inserted in the brass block, so I'm assuming it needs earthing in case the cartridge heater in the same block makes the block live? Excuse my ignorance.

For safety, if you can obtain/make a plastic cover for the SSR and the back of the PID controller that would be good too.

For initial testing, I'd replace your heater with a low wattage bulb.

The first test is that the LED on the SSR is illuminated when you think the heater should be turned on, and that the bulb lights. Both should be off otherwise.

Using the blue/brown wires for the low voltage wiring is confusing, but they seem to go to the correct places as far as I can tell.

Very useful test tips, and very helpful indeed overall, thank you very much. I've yet to tackle the PID instructions, which appear very challenging.

 

[(*steve*)]

Thank you for your feedback steve, much appreciated. Would connecting it to the heatsink under the SSR be appropriate? Any ideas as to how to do this with unravelling the protective braid?

Get some sort of metal cable clamp (P clamp) and pass the sensor cable through this. Attach it to something earthed and/or wire protective ground to the clamp.

It will be inserted in the brass block, so I'm assuming it needs earthing in case the cartridge heater in the same block makes the block live? Excuse my ignorance.

This is mains powered. Any exposed metal needs to be connected to mains earth.

 

[Blue]

Get some sort of metal cable clamp (P clamp) and pass the sensor cable through this. Attach it to something earthed and/or wire protective ground to the clamp.
This is mains powered. Any exposed metal needs to be connected to mains earth.

Understood. I think then I should change the main power lead for one that has an earth wire? and connect the thermocouple to that, which should earth the thermocouple and the brass block at the same time.

 

[(*steve*)]

Understood. I think then I should change the main power lead for one that has an earth wire? and connect the thermocouple to that, which should earth the thermocouple and the brass block at the same time.

Yes. That way if you have a fault you will blow a fuse or an RCD breaker rather than risking someone's life.

You never expect a fault like this, but you must always plan for one.

 

[Blue]

Thanks Steve. Invaluable advice.

 

[Blue]

Is it OK to shorten the length of the wire coming from a K Type thermocouple? 1 metre it comes with is too long, looking to reduce that by half.

 

[duke37]

You should not shorten the thermocouple if has a metal sheath. It will be sealed to stop moisture getting in.
If it is just two wires, then you can chop it down but getting a good connection to chromel/alumel can be difficult due to the surface oxide.

Why not just coil up the surplus?

 

[Blue]

Thanks Duke. I

You should not shorten the thermocouple if has a metal sheath. It will be sealed to stop moisture getting in.
If it is just two wires, then you can chop it down but getting a good connection to chromel/alumel can be difficult due to the surface oxide.

Why not just coil up the surplus?

Thanks Duke, I would like to reduce the cable/wire length, not the thermocouple unit itself. I appreciate they are a sealed unit. Any lead I cut short would retain the flexible wire sheaf. Sorry,i think I didn't explain well? I'd prefer not have a coil of wire coming from the thermocouple, they can be bought with different lengths of wire attached to them so I figured length of wire doesn't matter?

 

[duke37]

A thermocouple has a hot junction and a cold junction. In your case the hot junction will be the end of the thermocouple. The cold junction may be at the measuring device and perhaps held at a constant temperature, in this case, the cable will be compensating lead with similar properties to the thermocouple but cheaper and more flexible.
Sometimes the cold juction is at the cold end of the thermocouple and any extension will be twin copper.

You can cut down but if you extend, use the correct cable and make sure it is the right way round.

I do not think that you should be worried about the cold junction, a few degrees here or there will not make much difference for your job.

 

[Blue]

Thanks Duke.

You can cut down but if you extend, use the correct cable and make sure it is the right way round.

Thanks Duke. I won't be extending, though both wires are the same, so I'm not sure this cartridge heater is fussy about which way it is wired.

 

[duke37]

Thermocouple wires are not the same, the thermocouple produces a DC voltage and this must be connected the right way round unless you wish to control down to absolute zero !
All thermocouples I have seen either have coloured wires or a coaxial connector.

 

[Blue]

My error, sorry. They are indeed different. I have them wired to the correct poles on the controller. I was confusing the wires coming from the cartridge heater. They are the same on the cartridge heater, am trusting this is normal?

 

[duke37]

A heater is just a resistor which will get hot irrespective of the current direction. Your heater may run on AC where the dirction changes many times a second.

 

[Blue]

Thanks for your input to date.
So I finished this today. Wired a lamp to it, though didn't have an old style light bulb, had to use an energy saver., low watt. The lamp flashed at rapid regular intervals, like a pulse, so power getting through. Though the light on the SSR does not seem to come on as it was suggested it should. I wired the cartridge heater having seen that power was getting through to the lamp. The cartridge heater does not heat up at all.

So I can assume from this that a) the light on the SSR does not work and b) the cartridge heater is faulty.

Would I be correct??

 

[duke37]

I have not used an SSR so cannot comment on the light. Is this a led to indicate that it is enegised?

If the output can drive a fluorescent light, then there is output but fluorescent lights need a constant voltage input.
You can check the connection through the heater with an ohm meter. Disconnect it and see what the resistance is. Depending on the power, the resistance could be between 100 and 1000 ohms.

 

[Blue]

I have not used an SSR so cannot comment on the light. Is this a led to indicate that it is enegised?

If the output can drive a fluorescent light, then there is output but fluorescent lights need a constant voltage input.
You can check the connection through the heater with an ohm meter. Disconnect it and see what the resistance is. Depending on the power, the resistance could be between 100 and 1000 ohms.

Thanks Duke, but you lost me at ohm meter! I don't have such equipment I'm afraid.

The small light on the SSR has been mentioned previously, see below, by Steve. So I think it is meant to be on when power is going to the heater, which it is not, despite the lamp that is connected indicating power.

"The first test is that the LED on the SSR is illuminated when you think the heater should be turned on, and that the bulb lights. Both should be off otherwise."

 

[Blue]

OK, so bought an ohm meter.
The resistance through the cartridge heater is 177ohms. So think that is ok.
Nil voltage coming to the SSR from the PID controller, despite the 'OUT1' light being illuminated on the PID display.

At a dead end here, if my wiring is right (?). Then there's something in the settings of the PID, though the instructions are impossible, or the PID is faulty.

Here's a diagram how it's currently wired up, any errors?

 

[duke37]

There needs to be more information on the PID controller. If pins 3 and 4 are just connected together when the output is ON then there is no power to the SSR.

The mains does not have a + or - , it should be labelled L (line) and N (neutral).

As I said, I have not used SSRs but I thought that they used an led which may be polarity sensitive. You need the input parameters.