And here is what it looks like with a solenoid valve connected to the output:

Reference post #109.
After a second look at that image I think you can call this circuit fixed. Sure there are a couple of small glitches but the average voltage is almost 26 volts.
The image you show without a load is normal.

 

Just to confirm the MOC3063 should work.
I took out my old design with a MOC3033 (zcd, 250 PIV) driving a BTA06-600 Triac. The MOC3033 is the same as the MOC3063 except PIV is 250v.
It was originally designed for an 115v incandescent bulb. I simply swapped the bulb for a sprinkler solenoid, change the AC voltage to 24v, and the circuit worked as intended.

 

Just to confirm the MOC3063 should work.
I took out my old design with a MOC3033 (zcd, 250 PIV) driving a BTA06-600 Triac. The MOC3033 is the same as the MOC3063 except PIV is 250v.
It was originally designed for an 115v incandescent bulb. I simply swapped the bulb for a sprinkler solenoid, change the AC voltage to 24v, and the circuit worked as intended.

What resistance did you use for R1?

 

What resistance did you use for R1?

1 k ohms

 

1 k ohms

Is your circuit wired the same? Can you post the schematic?

 

Is your circuit wired the same? Can you post the schematic?

This was originally designed for 115VAC load.
All I did was change the load to 24VAC and connected a sprinkler solenoid.
It worked as intended. T1 is a BTA06-600 Triac.

 

Can you get an image of the waveform across the solenoid to compare with Mahonroy's circuit?

 

Can you get an image of the waveform across the solenoid to compare with Mahonroy's circuit?

Sorry...I was a little busy

This is a measurement across the solenoid coil.

 

This is a measurement across the solenoid coil.

Thank you.
There you go looks exactly like the image Mahonroy posted. As I said before the problem is fixed.

 

Will this triac circuit work with a 24VAC square wave? (e.g. +24VDC, -24VDC peaks, square).

I was not sure how the zero-crossing part would react.... if it would even matter?

 

As an alternative (if you must use AC) drive each solenoid from the DC bus using an H-bridge motor-drive circuit such as A4953. The losses will be lower.

 

OK, Everybody!
Now that the solenoids are being driven adequately, I am still wondering about what looks like a bit of oscillation near the peaks on the sine wave. I have a possible project lined up that would include driving about 24 sprinkler valves that would be controlling medium pressure compressed air. Sort of an air powered calliope, but quite a bit smaller than the steam powered ones.
The big difference is that this project is starting with a blank sheet of paper, not an existing control package.
The valves are rated for 24 volts AC, but I have had success running a 24 VAC solenoid gas valve on 12 volts DC from a battery during an extended power outage.

 

Will this triac circuit work with a 24VAC square wave? (e.g. +24VDC, -24VDC peaks, square).

24VAC is about 68 VPP
So it should work

I was not sure how the zero-crossing part would react.... if it would even matter?

As long as the load crosses zero (as would 68v PP) it should work.

 

A power square wave does not seem like a practical power source, where would it come from? Or is this a theoretical question?