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
Capacitors
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
Diodes
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
Any. Broadly-James "Silver" (Pet Warehouse # 505416, $33.88) 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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