Parts List for pH Meter-Controller

Resistors                       Value (1/4 watt, 5% tolerance)                         Part Number
-                                                                                      (Radio Shack)
R355                              47
R302                             100
R1, R500                         220
R351                             470
R453                              1k
R301                             10k
R2, R300, R352, R354, R451       10k potentiometer, 15 turn, pc-mount                         271-343
R3, R353                        4.7k
R400, R401, R450, R501           47k
R452                            220k
C451                           100pF
C352                         0.001uF     Must be low leakage.  272-126 ceramic works fine here (I used
                                         one),but use a low-loss polystyrene if available.
C303                          0.01uF
C1, C301, C302, C351, C4010    0.1uF
C450                             1uF electrolytic, Al or Tantalum                            272-1434
C350, C400                      10uF nonpolarized electrolytic                               272-999
C2                              10uF electrolytic
D500                          1N4001 (Non-critical)                                          276-1101
D450                          LED
Transitors, ICs
Q500                          IRF 510 MOSFET transistor                                      276-2072
U1                            LM317T IC Voltage Regulator                                    276-1778
U300, U400                    TL082 Dual JFET Op Amp                                         276-1715
Other stuff
pH probe                      Inexpensive Pinpoint brand from works fine
12 DC Power Supply            Make sure it can drive your valve if you're using one!         273-1652
                                                 works for me, but it won't drive a one Amp valve!
BNC Connector,  Jack          *Isolate from metal frame.  See notes.                         278-105
pH Display                    Any digital voltmeter.  Radio Shack's (special order)      RSU 11461498
                              panel meter is cheap and works fine, but the instruction sheet is awful!
Circuit Board                 0.1" grid pad-per-hole stock works well.                       276-158B
Housing                       Metal provides shielding.  See notes.   Waterproof? ;)
pH Buffers                    You will need pH 7.00 and pH 4.00 to calibrate (and periodically recalibrate)
                                your probe.
Stainless Steel Bolt          For optional grounding probe.  (See text.)

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