Although the thread is for a bypass valve, the used Bodine motor + controller would be simpler to control than a servo needle valve.
Procon pump replacement. Coming up with the DC supply shouldn't be too hard for you DSC since you know electronics.

Mark

dsc wrote:Hi Greg,

Oh one more question, do I need a one-way valve on the input of the pump, just before the tee to prevent backflow into the inline pipe (if I set the brew pressure to 3bar the 'other' 6bar will flow back to the input of the pump, won't it 'try' to flow against the inline water supply?).

Regards,
dsc.

There's pressure drop across the valve. Pressure on the outlet side of the pump will be at whatever the pump / bypass combination produces. Flow across the bypass valve experiences pressure drop to essentially the pump inlet pressure. So no additional check valve is required. I should point out, however, that there should be a check valve between the pump and the group, installed by the manufacturer. The bypass loop we're talking about must be installed upstream of the check valve (between pump and check valve). You will have to get creative with your plumbing if the check valve is mounted directly to the pump outlet. Shouldn't be too much trouble.

-Greg

dsc wrote:Hi Greg,

I agree that multi turn valves are harder to control (and too actually mount the servo so that it works), but one can always use a stepper motor to eliminate the use of encoders.

I looked at Swagelok fittings but they charge £14 for an ordinary brass 3/8" tee :O I can get all the compression/ordinary fittings from my local Screwfix for that amount of money!

Thanks for all the tips, I'll update this topic with some photos and results when it's up and running.

Oh one more question, do I need a one-way valve on the input of the pump, just before the tee to prevent backflow into the inline pipe (if I set the brew pressure to 3bar the 'other' 6bar will flow back to the input of the pump, won't it 'try' to flow against the inline water supply?).

Regards,
dsc.

We've done the stepper motor thing here at work for a variety of motion control apps, but I really hate it when folks here don't wanna pony up for an encoder because stepper motor systems have a habit of losing their zero position (losing steps) and ya gotta go through all kinds of contortions to re-initialize them without an encoder. WRT the stepper motor / encoder / cobbling it together thing, by the time you fool around with it this much you should just buy a fluid-0-tec TMFR pump with analog variable speed controller, a pressure transducer, programmable process controller and do the damn thing right. You could write your own Labview code and leave out the process controller, but that costs time and you'll have to have something to read the transducer and send the data to the accompanying computer. Personally I think all that sh** looks good in any modern kitchen, but my coffee stuff (except the roaster) is in debasement - at Espresso Research LLC corporate headquarters. The roaster is in the laundry room.

-Greg

Hi guys,

I might try the motor approach sometime in the future, although now I'd like to go down the bypass route and simply test it out.

Out of curiosity, will the size of the fittings affect anything in the system? I need to use some 1/2" compression/threaded fittings and will have to use 1/2" - 3/8" reductions. Would that be a problem? It is possible to use dedicated 3/8" threaded air fittings, but there's no easy way to connect various parts of the bypass system using flexible hoses. With 1/2" fittings I can simply use flexible tap connectors which are cheap and easily available.

Regards,
dsc.

Just as a note, I was in my electronics store yesterday. They just had gotten in a box of rotary encoders with 25 pulse per revolution, with a 1/4 in shaft fitting, just 5 bucks. I am not sure if 15deg would be accurate enough for a needle valve pressure profile. But it's just a thought.
-Cecil

another_jim wrote:Andy and Greg were looking for precise and programmable systems

Yes. For home barista use, manual profiling systems can be practical, fun and educational. Home baristas have the time to obsess over every moment of every shot.

But my original emphasis (and I think Greg's, too) was for commercial operation. In a cafe you want to find a profile that gives good results, program it into your system, and let the electronic brain repeat it time after time. No cafe barista can afford to stand there nursing each shot through a manual profile.

Hi guys,

of course a manual system is simply a way to see how pressure profiling affects the espresso, it's not really a long term solution as one cannot easily recreate the same profile. But if this bypass approach works I will try to add a uC based HMI to allow programming, using pre-set profiles and full manual (via a knob) operation.

Regards,
dsc.

Hi guys,

I got the bits today and will be testing out the manual operation after work. The only thing I'm a bit worried is the ball valve itself which seems to be lubricated with some rather smelly grease/oil. Do you think it's going to be a problem, ie. the water is going to taste different when passing the valve? I'd say no as it is hot/cold water approved, but maybe I should switch to something more food safe?

Regards,
dsc.

Seeing as half of taste is smell would you want to risk your machine getting a smell as you describe it? Not quite boiling water at 9 bar may not have registered to the Mfg as 'hot water'. Just a thought.

CRCasey wrote:Not quite boiling water at 9 bar may not have registered to the Mfg as 'hot water'. Just a thought.

The water would be "cold" tap water- hot water doesn't go through the pump.