PID and solenoid gas valve.

[10x]

I got the bright idea of using a PID and a 12V solenoid gas valve to regulate the temperature on a propane pot.
The PID does not generate enough amps to operate the solenoid, so I went to a SSR and a 12 volt battery. The solenoid heats up more than it should when direct wired to the battery. To solve this I put in an element from a sandwich maker (about 200 watts) as a resistor - too much resistance as it will not trip the solenoid and turn on the valve. It will keep the valve locked on once the valve is tripped.
I will be trying out 12V auto bulbs to increase resistance in lieu of the element....(buying a resistor may be easier).


The real problem is that the solenoid stays on when the power to it is cut by the SSR. I have to physically break the circuit and then the solenoid shuts off.
Is the SSR leaking a bit of power?

This project looks like it has potential - the PID reads the alloy temp very nicely and sends and turns the signal on and off at the correct temps - the solenoid gas valve just does not cooperate.

[RED333]

The coil in the valve will heat up a bit, you need a relay, not a SSR.
So what relights the burner when it calls on?
I am guessing some kind of pilot.

[xacex]

I use a hot water heater solenoid on my brew system that uses 24v. The pid controls the transformer, and it seems to work well. SSR inline to the transformer has not given me the overheating issue you are having. A battery is something I have not tried so I can't help you on that end, but the solenoid only requires .5 amp at most so finding a transformer should not be an issue. Nice little glow with the pilot jet, but it will scare children when the ring fires up pumping 200,000 BTU to the bottom of the HLT. A little more than what a lead pot needs. Nice project for someone who want to use natural gas instead of electricity, but electricity is still cheaper here on the west coast. I freeze propane tanks to the neck when I am going full bore.

[10x]

I use a hot water heater solenoid on my brew system that uses 24v. The pid controls the transformer, and it seems to work well. SSR inline to the transformer has not given me the overheating issue you are having. A battery is something I have not tried so I can't help you on that end, but the solenoid only requires .5 amp at most so finding a transformer should not be an issue. Nice little glow with the pilot jet, but it will scare children when the ring fires up pumping 200,000 BTU to the bottom of the HLT. A little more than what a lead pot needs. Nice project for someone who want to use natural gas instead of electricity, but electricity is still cheaper here on the west coast. I freeze propane tanks to the neck when I am going full bore.

Thank you, this should solve it nicely....
We must get a better quality of propane here - I run with a regulator with about 4 - 5 oz of pressure and get a fairly fast melt.
My goal is to keep temperatures under 600 F when melting wheel weights so that zinc does not go into the melt.

The pilot is from an old water heater. I put a " T " in the propane line with a valve to reduce flow. It works well.
I am considering using a valve from an old water heater, a 1.5 volt battery run through an PID internal relay (replacing the thermopyle) instead of the solenoid valve. I believe this would require the relay to send a signal to shut off the gas when the target temperature is reached.

I think I have found a way to safely remove zinc from lead using sulfur and a CO2 flood over the alloy (no O2 means the sulfur does not burn) - I am still going to take all precautions to minimize any risk if the sulfur does burn. (Fume hood with powered exhaust ventilation).

And there is a way to reduce antimony ( using sodium) so the lead can be softer for Hollow base bullets for my .455 webley.
Temperature control is critical in both processes.

[bangerjim]

Use an interposing mechanical relay (like a Potter Brumfield) and not an SSR. The coil on your solenoid is probably designed for AC and NOT(!) DC. 12VDC will overhead a coil made for AC. Switch to a hard contact relay and use 12 VAC.

Also put a MOV across the coil of the relay to stop the "field collapse" of the coil that could burn out the driver circuit in your controller if it uses a solid state output rather than a dry contact relay (depends on brand and design).

Personally I would never attempt this approach on a simple lead pot, even though I am an engineer and design and sell controller based equipment and processes. Everybody on here seems to think a PID-based electronic controller is God's gift to lead melters....and now are spreading to ovens and other simple stuff.

Simple is better in many cases!

banger

[Lee]

MOV's are voltage rated. Specify what voltage you need for your application. (A 220V MOV won't work!) Reverse diodes might prevent "field collapse also"?? Just sayin!

[bangerjim]

MOV's are voltage rated. Specify what voltage you need for your application. (A 220V MOV won't work!) Reverse diodes might prevent "field collapse also"?? Just sayin!


Yes the MOV must be selected for the application. I am not playing design engineer here......I get paid for that in the real world!

But the field collapse is a serious consideration with solid state outputs.

User beware. That is why an interposing relay is the safest way to do this. (many have surge protection already built in for the correct voltage of the coil). Again, depends on the design of the controller.

Stick with elecric heater lead pots and not solenoid valves!

banger