Pressure regulator for the PEM cell

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Alexander Lichte
Posts: 12
Joined: Sat Jan 08, 2022 5:09 am
Real name: Alexander Lichte

Pressure regulator for the PEM cell

Post by Alexander Lichte »

If you try to "directly feed" the PEM cell to the fusor, you need to keep the pressure inside the D2 part at ambient to avoid contamination.

I built a controller for that.
I measure the D2 pressure with a differential pressure sensor XPC0.3GFSH and drive the PEM cell current so that the D2 pressure stays at ambient pressure.
PEM_Reg_shematic_1.0.png
The signal of the XPC sensor is amplifiered and compared with 2.5V at the PI-regulator. 2.5V means "ambient pressure".
The output of the PI regulator drives a current source for the PEM cell.
Please supply that device with 5Vdc.

The construction:
IMG_4816_kl.JPG
I insert an ampere meter in series to the PEM. I can measure the gas flow on this was very precise:
IMG_4822_kl.JPG
It's a complete LTspice simulation with gas flow simulation. I do not know, how to upload this file.
Therefore I post it as plain text. You can copy this text in something like "pressuresim.asc" and run it with LTspice.

Code: Select all

Version 4
SHEET 1 1892 1012
WIRE 1072 -112 1056 -112
WIRE 1104 -112 1072 -112
WIRE -80 -48 -96 -48
WIRE -32 -48 -80 -48
WIRE 48 -48 -32 -48
WIRE 192 -48 48 -48
WIRE 288 -48 272 -48
WIRE 352 -48 288 -48
WIRE 1104 -48 1104 -112
WIRE 48 -32 48 -48
WIRE 192 -32 192 -48
WIRE 464 -32 416 -32
WIRE 480 -32 464 -32
WIRE 576 -32 480 -32
WIRE 672 -32 656 -32
WIRE 352 -16 336 -16
WIRE 464 -16 464 -32
WIRE 384 16 384 0
WIRE 768 16 736 16
WIRE 784 16 768 16
WIRE 816 16 816 -32
WIRE 736 32 736 16
WIRE -96 48 -96 -48
WIRE 672 48 672 -32
WIRE 704 48 672 48
WIRE 816 64 816 16
WIRE 816 64 768 64
WIRE 48 80 48 48
WIRE 80 80 48 80
WIRE 272 80 272 -48
WIRE 272 80 160 80
WIRE 336 80 336 -16
WIRE 464 80 464 64
WIRE 464 80 336 80
WIRE 544 80 464 80
WIRE 704 80 672 80
WIRE 464 96 464 80
WIRE 1104 96 1104 32
WIRE 816 128 816 64
WIRE 880 128 816 128
WIRE 544 144 544 80
WIRE 768 144 752 144
WIRE 784 144 768 144
WIRE 960 144 944 144
WIRE 880 160 848 160
WIRE 192 176 192 48
WIRE 288 176 192 176
WIRE 352 176 288 176
WIRE 48 192 48 80
WIRE 192 192 192 176
WIRE 432 192 416 192
WIRE 464 192 464 176
WIRE 464 192 432 192
WIRE 912 192 912 176
WIRE 944 192 912 192
WIRE 960 192 944 192
WIRE 352 208 336 208
WIRE 464 208 464 192
WIRE 416 224 384 224
WIRE 432 224 416 224
WIRE 672 240 672 80
WIRE 752 240 752 224
WIRE 752 240 672 240
WIRE 752 256 752 240
WIRE -96 288 -96 128
WIRE 48 288 48 272
WIRE 128 288 48 288
WIRE 192 288 192 272
WIRE 192 288 128 288
WIRE 848 288 848 160
WIRE 1056 288 848 288
WIRE 1104 288 1104 192
WIRE 1104 288 1056 288
WIRE 336 304 336 208
WIRE 464 304 464 288
WIRE 464 304 336 304
WIRE 544 304 544 224
WIRE 544 304 464 304
WIRE 1104 304 1104 288
WIRE 464 320 464 304
WIRE 544 320 544 304
WIRE 128 336 128 288
WIRE 752 352 752 336
WIRE 1104 400 1104 384
WIRE 512 416 496 416
WIRE 544 416 544 400
WIRE 544 416 512 416
WIRE 64 688 -48 688
WIRE 208 688 64 688
WIRE 368 688 208 688
WIRE 512 688 368 688
WIRE 368 704 368 688
WIRE -48 720 -48 688
WIRE 208 736 208 688
WIRE 512 784 512 768
WIRE -48 816 -48 800
WIRE 208 816 208 800
WIRE 368 816 368 784
FLAG 384 -64 0
FLAG 384 160 0
FLAG -96 288 0
FLAG -80 -48 V5V
FLAG 384 16 V5V
FLAG 416 224 V5V
FLAG 480 -32 Out
FLAG 432 192 Mid
FLAG 288 -48 In+
FLAG 288 176 In-
FLAG 512 416 V5V
FLAG 464 400 0
FLAG 1104 400 0
FLAG 1072 -112 V5V
FLAG 768 144 V5V
FLAG 912 112 0
FLAG 944 192 V5V
FLAG 1056 288 Ucur
FLAG 752 352 0
FLAG 736 96 0
FLAG 768 16 V5V
FLAG 816 16 PIout
FLAG -48 816 0
FLAG 208 816 0
FLAG 512 864 0
FLAG 64 688 Pressure
FLAG 368 816 0
FLAG 128 336 0
FLAG 384 288 0
FLAG 912 256 0
FLAG -32 16 0
SYMBOL Misc\\EuropeanResistor 176 -48 R0
SYMATTR InstName RM2
SYMATTR Value 3k2
SYMBOL Misc\\EuropeanResistor 32 -48 R0
SYMATTR InstName RM1
SYMATTR Value 3k2
SYMBOL Misc\\EuropeanResistor 176 176 R0
SYMATTR InstName RM3
SYMATTR Value 3k2
SYMBOL Misc\\EuropeanResistor 32 176 R0
SYMATTR InstName RM4
SYMATTR Value 3k2
SYMBOL Opamps\\UniversalOpamp2 384 -32 M180
SYMATTR InstName U1A
SYMBOL Opamps\\UniversalOpamp2 384 192 M180
WINDOW 0 -36 40 Left 2
SYMATTR InstName U1B
SYMBOL Misc\\EuropeanResistor 480 192 R180
WINDOW 0 31 76 Left 2
WINDOW 3 31 40 Left 2
SYMATTR InstName R1A
SYMATTR Value 100k
SYMBOL Misc\\EuropeanResistor 480 304 R180
WINDOW 0 32 54 Left 2
WINDOW 3 31 40 Left 2
SYMATTR InstName R1B
SYMATTR Value 100k
SYMBOL Misc\\EuropeanResistor 480 80 R180
WINDOW 0 31 76 Left 2
WINDOW 3 31 40 Left 2
SYMATTR InstName R2A
SYMATTR Value 100k
SYMBOL Misc\\EuropeanResistor 480 416 R180
WINDOW 0 31 76 Left 2
WINDOW 3 31 40 Left 2
SYMATTR InstName R2BA
SYMATTR Value 200k
SYMBOL Misc\\EuropeanResistor 560 240 R180
WINDOW 0 31 76 Left 2
WINDOW 3 31 40 Left 2
SYMATTR InstName RGain
SYMATTR Value 2k2
SYMBOL voltage -96 32 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL Misc\\EuropeanResistor 560 416 R180
WINDOW 0 31 76 Left 2
WINDOW 3 31 40 Left 2
SYMATTR InstName R2BB
SYMATTR Value 200k
SYMBOL current 368 704 R0
WINDOW 0 32 40 VTop 2
WINDOW 3 -32 40 VBottom 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName I1
SYMATTR Value 600µ
SYMBOL Opamps\\UniversalOpamp2 912 144 M180
WINDOW 0 24 -16 Left 2
SYMATTR InstName U2B
SYMBOL npn 1040 96 R0
SYMATTR InstName Q1
SYMATTR Value BC847B
SYMBOL Misc\\EuropeanResistor 1088 288 R0
SYMATTR InstName R3
SYMATTR Value 10
SYMBOL Misc\\EuropeanResistor 736 240 R0
SYMATTR InstName R4
SYMATTR Value 33k
SYMBOL Misc\\EuropeanResistor 736 128 R0
SYMATTR InstName R5
SYMATTR Value 33k
SYMBOL Opamps\\UniversalOpamp2 736 64 R0
SYMATTR InstName U2A
SYMBOL cap 736 -48 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 10µ
SYMBOL voltage 1104 -64 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 0 -69 11 Left 2
SYMATTR InstName V_PEM
SYMATTR Value 2
SYMBOL Misc\\EuropeanResistor 944 160 R270
WINDOW 0 27 56 VTop 2
WINDOW 3 5 56 VBottom 2
SYMATTR InstName R6
SYMATTR Value 1k
SYMBOL Misc\\EuropeanResistor 560 -16 R270
WINDOW 0 27 56 VTop 2
WINDOW 3 5 56 VBottom 2
SYMATTR InstName R7
SYMATTR Value 100k
SYMBOL bi2 -48 720 R0
SYMATTR InstName B1
SYMATTR Value I=I(V_PEM)*0.116
SYMBOL cap 192 736 R0
SYMATTR InstName C2
SYMATTR Value 5
SYMBOL bv 176 80 R90
WINDOW 0 -32 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName B2
SYMATTR Value V=V(Pressure)
SYMBOL voltage 512 768 R0
WINDOW 3 -51 136 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PULSE(0 -1 2 1 1 29 60)
SYMBOL Misc\\EuropeanResistor 720 -16 R270
WINDOW 0 27 56 VTop 2
WINDOW 3 5 56 VBottom 2
SYMATTR InstName R9
SYMATTR Value 330k
SYMBOL Misc\\EuropeanResistor 528 784 R180
WINDOW 0 31 76 Left 2
WINDOW 3 31 40 Left 2
SYMATTR InstName R8
SYMATTR Value 200
SYMBOL cap 368 224 R0
WINDOW 0 -19 31 Left 2
WINDOW 3 -18 45 Left 2
SYMATTR InstName C3
SYMATTR Value 100n
SYMBOL cap 896 192 R0
SYMATTR InstName C4
SYMATTR Value 100n
SYMBOL cap -48 -48 R0
SYMATTR InstName C5
SYMATTR Value 10µ
TEXT -120 416 Left 2 ;https://www.wikiwand.com/de/Instrumentenverst%C3%A4rker
TEXT -112 392 Left 2 ;Ua=(1+R2/R1+2*R2/RGain)*(U2-U1)
TEXT 704 488 Left 2 !.tran 100
TEXT 336 -56 Left 2 ;3
TEXT 336 168 Left 2 ;5
TEXT 688 72 Left 2 ;3
TEXT 864 120 Left 2 ;5
TEXT 336 -24 Left 2 ;2
TEXT 336 200 Left 2 ;6
TEXT 688 40 Left 2 ;2
TEXT 864 152 Left 2 ;6
TEXT 424 -40 Left 2 ;1
TEXT 776 56 Left 2 ;1
TEXT 408 176 Left 2 ;7
TEXT 952 136 Left 2 ;7
TEXT 376 0 Left 2 ;8
TEXT 928 112 Left 2 ;8
TEXT 392 -56 Left 2 ;4
TEXT 920 176 Left 2 ;4
TEXT 416 -56 Left 2 ;TLC272
TEXT 360 128 Left 2 ;TLC272
TEXT 720 120 Left 2 ;TLC272
TEXT 856 184 Left 2 ;TLC272
TEXT 88 -136 Left 2 ;XPC0.3GFSH\ndiff.pressure\nsensor
TEXT 136 312 Left 2 ;1
TEXT 240 72 Left 2 ;2
TEXT 24 -128 Left 2 ;3
TEXT 240 168 Left 2 ;4
TEXT -88 512 Left 2 ;11.2l H2 benoetigen 96485As (https://www.chemie.de/lexikon/Elektrolyse.html)\n==> 1A => 0.116ml/s
TEXT 0 768 Left 2 ;Flow rate in ml/s
TEXT -88 568 Left 2 ;Electric Units:  Pneumatc Units:\n1A                     1ml/s prod. Gas Volume at 1000mbar\n1V                     1000mBar pressure  (0V=ambient)\n1F                     1ml Volume of gas container \n1/Ohm              Nozzle through which a volume of 1ml/s flows at 1000mBar
TEXT 488 888 Left 2 ;Flow Stimuli
TEXT 312 848 Left 2 ;Leakage of PEM cell
TEXT 88 136 Left 2 ;Approx.\n1mV/mBar \nat XPC0.3
TEXT 152 456 Left 4 ;Pneumatic model
TEXT 368 -136 Left 2 ;Diferential\nAmplifier
TEXT 656 -128 Left 2 ;PI-Regulator
TEXT 880 -128 Left 2 ;Current Source
TEXT 904 864 Left 2 ;PEM cell pressure regulation\nRev. 1.0\n29.04.2022   / Alex. Lichte
TEXT 640 256 Left 2 ;2.5V=Ambient
TEXT 1040 8 Left 2 ;PEM\ncell
TEXT 192 840 Left 2 ;Gas\ncontainer
TEXT -72 848 Left 2 ;Gas flow\nof PEM cell
RECTANGLE Normal 256 320 16 -144 2
RECTANGLE Normal 1152 48 1024 -80 2
RECTANGLE Normal 640 928 -112 432 2
RECTANGLE Normal 576 432 256 -144 2
RECTANGLE Normal 832 432 576 -144 2
RECTANGLE Normal 1168 432 832 -144 2

JoeBallantyne
Posts: 133
Joined: Tue Jul 20, 2010 4:08 pm
Real name: Joe Ballantyne
Location: Redmond, WA

Re: Pressure regulator for the PEM cell

Post by JoeBallantyne »

Or you can just use the PEM to fill a syringe with D2 gas, and then connect that to the fusor through a needle valve, leak valve or mass flow controller. Ok, it means you have an extra manual step to switch the syringe from the PEM to the fusor gas input, but it obviates the need for your device.
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Richard Hull
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Posts: 13986
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Pressure regulator for the PEM cell

Post by Richard Hull »

Still, this is a nice kludge and work around.........If it successfully does fusion in a controlled many on a home built fusor!

The circuit looks like something I would wire up to test an idea out. Thanks for sharing.

Now that differential pressure item. I have a couple of those surplus.... but others here??? There is always a key component that is not cheap.
The bell jar did a kludge way back using an electrically controlled injector.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.
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Rich Feldman
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Joined: Mon Dec 21, 2009 6:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: Pressure regulator for the PEM cell

Post by Rich Feldman »

Nice work, Alexander.
I especially like your very compact breadboard construction of the circuit.
And your point that simple ammeter in series with PEM cell tells the mass flow,
in my opinion more accurately than any MFC.

Do you know the range of pressure which those PEM demonstrator cells can tolerate?
It depends on mechanical support of the membrane.

The electrolyzers for refilling metal hydride H2 storage cartridges work at up to +30 bar (over 400 psi). Here's one familiar brand, apparently with a new web look.
https://www.h2planet.eu/nl/detail/HydrofillPRO

A PEM electrolyzer which could tolerate strong vacuum on the hydrogen side would be very handy for fusors. Gas flow controlled directly by cell current. No need for any flow restrictors or sensors and feedback.
All models are wrong; some models are useful. -- George Box
User avatar
Alexander Lichte
Posts: 12
Joined: Sat Jan 08, 2022 5:09 am
Real name: Alexander Lichte

Re: Pressure regulator for the PEM cell

Post by Alexander Lichte »

Running the PEM cell close to vacuum can cause problems:
The Nafion foil is very wet (O2 side filled with D2O) and I am afraid of a lot of evaporation.
But maybe keeping a slight overpressure on the D2 side is an advantage? Unfortunately I don't know that either.

Something else:
If you set a higher current than 100mA (smaller R3), Q1 should be replaced with a stronger transistor.
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