Thanks Jim, that is good news then. I could have just mounted the SSR to the side of a metal box and not had the heatsink. Thanks for the information.

So I found a NOS Omega CN77232-C4 on eBay on a $72 BIN or make an offer. They took $50 for it. It's got the RS-485 connection built in, so I can move this to more advanced projects in the future (like maybe a temp logger and PID control for a roaster). I'll have to do some trickery in the wiring, since it has a 1A SSR on output one and a 5A relay on output two. The manual shows how to wire the relay out to control an SSR, so I'll probably do that and set the cycle time to 20-30 seconds to spare the relay some (the Caravel doesn't lose heat so quickly and a 20 second cycle should be stable enough).

Now I just need the Pt100 RTD and a couple of hours to put it all together.

GVDub wrote:I'll have to do some trickery in the wiring, since it has a 1A SSR on output one and a 5A relay on output two. The manual shows how to wire the relay out to control an SSR....

That PID config is going to make things a little complicated.

Jim

JimG wrote::roll: That PID config is going to make things a little complicated.

Jim

Yeah, and I'll probably end up getting one of the Auberins PID controllers with the SSR control output at some point, but the Omega is a real quality device and this one is new in the box with the serial communication option, and an absolute steal at the price I got. Since the mechanical relay on the Omega actually has enough capacity to handle the Caravel and I can keep the cycle time long enough not to put too much wear on it, I can save the SSR that I have for a second PID unit for the Caravel Ursula I'm using at work.

Yes, I have a tendency to over-complicate things. I think I read too many Rube Goldberg cartoons as a kid.

GVDub wrote:I just hope this doesn't end up being like my friend who used to drive a Rover TC2000. He had to keep 4 of them just to have one on the road running at any given time.

When I had a '67 "E Type" Jag convertible, that was my general sentiment. 1 to drive, while 1 is in the shop.

IMAWriter wrote:When I had a '67 "E Type" Jag convertible, that was my general sentiment. 1 to drive, while 1 is in the shop.

Ahhh, British Leyland Motors, home of fine quality control.

Bit late in this post I know but:

I have recently worked on several Caravel thermostats. usually I find it is just a matter of calibrating it correctly. You don't need to take many things apart:

1) remove the kettle and base

2) turn the power knob to 'on' position

3) turn the thermostat screw to approximately the middle position- you can see the end of the screw protruding (below the kettle release catch) onto what I will call the 'switching lever'. This is the important part- it is a basic see-saw with the on switch at one end- and the thermostat screw at the other- the fulcrum is at the thermostat switch.

4) when the machine is working correctly- at this time you should be able to able to press both the 'on' knob- and the thermostat screw- alternately- switching the lever back and forth- you should here a definite click as you do this- this is the switching lever activating the thermostat switch. You should hear the same click when you turn the 'on' knob on and off. If you don't here the click- you can adjust the movement of the 'switching lever' via the thermostat screw- and via a small screw located directly behind the on switch- inside the base- above the power cable. You can get a small driver in there without changing any of the wiring. Basically the adjustment should be simple- turn the two screws to try and find the center point and have the switch operating. If there is little movement in the see-saw- adjust it until it start rocking. There may be no click and it seems like the switch is dead- then you hit the sweet spot! Once you get the lovely 'click, click' you know you have it right. Also now the on/off switch should work correctly.

5) Reassemble and test- adjust the thermostat to taste with subtle adjustments only. Allow the machine to cool- then make a small adjustment- retest. I try and set mine so they switch out just after a medium rolling boil.

6) your all cool to go.

DISCLAIMER

if you cannot get a nice click- you have failed- or the switch has failed. I have yet to find a failed switch. Sometimes you need to push on the back of the switch and little with a driver to get it clicking nicely- it seems they may stick with storage. Once unstuck they seem fine.

Unfortunately, my problem is that the microswitch immolated itself, leaving nothing behind but carbon and a memory. So, a PID controller seems like it might be easier than trying to source a new microswitch.

As a side note, while visiting my brother in New Mexico, I found a great project box for the PID at Los Alamos Sales Company, better known as 'The Black Hole'. They're a surplus/junk warehouse that sells all the electronic tidbits and detritus from the Los Alamos Atomic Labs (you want one of the mechanical calculators used on the Manhattan Project? They got 'em). The box is a slant front instrumentation chassis, so it's somewhat larger than I strictly need, but it will look cool, be easy to work on, and has the added cachet of being a little piece of history.

sorrentinacoffee wrote:Bit late in this post I know but:

I have recently worked on several Caravel thermostats. usually I find it is just a matter of calibrating it correctly. You don't need to take many things apart:

1) remove the kettle and base

2) turn the power knob to 'on' position

3) turn the thermostat screw to approximately the middle position- you can see the end of the screw protruding (below the kettle release catch) onto what I will call the 'switching lever'. This is the important part- it is a basic see-saw with the on switch at one end- and the thermostat screw at the other- the fulcrum is at the thermostat switch.

4) when the machine is working correctly- at this time you should be able to able to press both the 'on' knob- and the thermostat screw- alternately- switching the lever back and forth- you should here a definite click as you do this- this is the switching lever activating the thermostat switch. You should hear the same click when you turn the 'on' knob on and off. If you don't here the click- you can adjust the movement of the 'switching lever' via the thermostat screw- and via a small screw located directly behind the on switch- inside the base- above the power cable. You can get a small driver in there without changing any of the wiring. Basically the adjustment should be simple- turn the two screws to try and find the center point and have the switch operating. If there is little movement in the see-saw- adjust it until it start rocking. There may be no click and it seems like the switch is dead- then you hit the sweet spot! Once you get the lovely 'click, click' you know you have it right. Also now the on/off switch should work correctly.

5) Reassemble and test- adjust the thermostat to taste with subtle adjustments only. Allow the machine to cool- then make a small adjustment- retest. I try and set mine so they switch out just after a medium rolling boil.

6) your all cool to go.

DISCLAIMER

if you cannot get a nice click- you have failed- or the switch has failed. I have yet to find a failed switch. Sometimes you need to push on the back of the switch and little with a driver to get it clicking nicely- it seems they may stick with storage. Once unstuck they seem fine.

Nice description - Is the inside the same as this from Walter?: img/heimroester-at-mathoms-caravel-thermostat-s.jpg

Larger photo: http://heimroester.at/mathoms/caravel/thermostat.jpg
It would be great if you could pair your description with Walters photo.