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Battery Discharger/Capacity Meter (2)

keyboard, discharger and assembly

Battery Discharger/Capacity Meter (2)
To enable the control module, described in Part 1, to function as a battery discharger, a number of additional hardware components are required. First, of course, is the keyboard for the entry of data and second, a printed circuit board with the actual discharger itself. A nice design aspect of this project is that the hardware can be tested with the aid of a few diagnostic programs.KeyboardA small keyboard is required to enable the entry of user information. Our approach has been a readymade keyboard with 12 buttons. Each key has an individual as well as a common connection. Because the control module can measure analogue voltages, it suffices to fit a voltage divider for each key. The schematic of this is shown in Figure 5. The table below the figure lists the key symbols. The second line indicates the resistor value for each key and the third line shows the resulting hex value that will be obtained when the key is pressed.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list
(Discharger board)
R1 = 1kOhm
R2,R10,R12 = 10kOhm
R3 = 100kOhm
R4 = 220Ù
R5 = 16kOhm 2
R6 = 48kOhm 7
R7 = 97kOhm 6
R8 = 18kOhm
R9 = 22kOhm
R11 = 56kOhm
R13-R16 = 1O, 0.5W
P1 = 25kOhm preset
P2 = 100kOhm preset
C1,C4,C5 = 100nF ceramic
C2 = 220µF 25V radial
C3 = 100µF 50V radial
C6 = 470pF
D1 = 1N4148
D2 = LED, red, high efficiency
T1 = BC517
T2,T3 = BS170 (or BSN10A)
T4 = BUZ100
IC1 = LP2950CZ5.0
IC2 = CA3130
K1,K5 = 3-way SIL pinheader
K2,K6 = 2-way pinheader
K3 = 2-way PCB terminal block, lead pitch 5mm
K4 = 5-way pinheader
F1 = fuse 3.15 A (fast) with PCB mount holder
PCB, order code 010201-2 (supplied together with control board 010201-1)
Diskettes, project software, order code 010201-11
- enclosure, e.g., Teko desk type 362
- heatsink for T4: Fischer SK132/37.5/SA
- fan, 40 x 40 mm, 12 Vdc
- mains adaptor, 300 mA, 6-12 Vdc,
- wander socket, red
- wander socket, black
- keyboard, 12 keys, 1 common connection, 12 individual connections, e.g., Display Electronics # 03.52.1252 or Conrad Electronics # 19-55-61
- miniature slide switch, 2 x changeover
- turned pin socket strip, lead pitch 2.54mm
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