Michel Kuenemann
About the article

Automatic Running-in Bench, part 1

for internal combustion model engines

Automatic Running-in Bench, part 1

Even though brushless electric motors have largely replaced internal combustion engines in small- and medium-sized radio-controlled model aircraft, many model enthusiasts are still attached to internal combustion (i/c) engines and these need to be run in before they can go airborne. This ambitious project automates this important operation.

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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.

Extra info / Update

Technical specifications
- 32-bit ARM7 processor running at 59 MHz, 128 kB flash memory and 64 kB RAM.
- Throttle control by standard model servo. Configurable travel and direction of movement.
- Microcontroller-driven glow plug heating.
- Engine speed measurement from 0 to over 30,000 rpm.
- Engine temperature measurement from 0–160 °C.
- Ambient temperature measurement
- Mixture adjustment managed by the on-board software.
- Mobile pocket terminal with 4-line / 20 character alphanumeric LCD display, push buttons and encoder knob.
- USB link
- Direct Servo Control (DSC) interface
- Emergency stop push button
- Power supply: 7–15 Vdc



March 17, 2009. Corrections

1. Page 31, central column, line before header “Construction”. Text should read:

And lastly, the terminal's LCD backlight is controlled by a P-channel MOS transistor.


2. At the beginning of the paragraph "Testing the pocket terminal (GMMI)", 'JP8' should read 'JP6'.


3. D10 in drawing 080253-14 (main schematic) should be 3V3 , not 5V6.


4. Do not to use a readymade 'type 1'  RJ6 cable (crossed wires!) to hook up the pocket terminal to the main board, but a straight 1-on-1 cable. This is also known as '6 pole 6 connector RJ11 plug to plug modular cable, Straight-Reverse' (pin1 to pin1, pin2 to pin2… pin6 to pin6). This cable will be included in the kit for the project.


Component list
Board # 080253-1

(0.25W 5%)
R1...R4, R7, R9, R48, R58 = 47kOhm
R5, R6, R26, R32, R33, R45, R47 = 10kOhm
R8, R25, R49, R50...R53 = 2kOhm2
R10, R11, R24, R27 = 220Ohm
R12, R13, R17, R18, R28, R34, R39 = 5kOhm6
R14, R15, R16, R19, R20, R29, R35, R38, R40, R41, R44, R46 = 1kOhm
R21, R22, R23 = 100Ohm
R31 = 39kOhm
R36 = 180Ohm
R37 = 390Ohm
R42 = 1kOhm5
R43 = 22kOhm

(0.25W 1%)
R30 = 90kOhm9

(1W 5%)
R54, R55 = 22Ohm


C1, C8, C14, C18, C21, C25, C28 = 47uF 63V, electrolytic radial, lead pitch 2.54mm
C22, C37 = 470uF 35V, radial electrolytic, lead pitch 5mm (0.2”)
C33 = 220uF 16V, radial electrolytic, lead pitch 2.54mm (0.1”)
C26 = 47uF 10V, tantalum, case C (Kemet: T491C476K010AT)
C2...C7, C9...C13, C15, C16, C17, C19, C20, C23, C24, C27, C29...C32, C34, C35, C36 = 100nF / 50V, ceramic, lead pitch 2.54mm (0.1”)


D1, D11, D12 = 1N5822, Schottky diode, 3A, 40V
D2, D5, D16, D17, D18, D19 = 3V9, 0.5W, zener diode
D4 = 1V4, 0.5W, zener diode
D6, D7,D8,D9 = 5V6, 0.5W, zener diode
D10 = 3V3, 0.5W, zener diode
D14 = 9V1, 0.5W, zener diode
D3, D15 = LED, red, low current, 3mm (0.12”)
D13 = LED, green, low current, 3mm (0.12”)

IC1 = FT232RL, SSOP28
IC2 = LM3724IM5-3.08, SOT23-5
IC3, IC4 = PCA9517A, SO8
IC5 = LM2940CT-5.0, TO220
IC6 = AD7417ARZ, SO16
IC7 = TLC272, DIP8
IC8 = ULN2804AFWG, SOL18

T2, T4, T5 = BC547B, TO92
T3 = BC557A, TO92

JP1…JP10, JP12 = 2-way pinheader, lead pitch 2.54mm (0.1”)
JP11, K5 = 3-way pin header, lead pitch 2.54mm (0.1”)

K1, K3 = 2x10-way flat cable socket
K2 = USB type B socket, PCB mounting
K4, K15, K17 = 2-way polarized vertical header, wire-to-board, lead pitch 2.54mm (0.1”) (Farnell # 588570)
K6, K7, K8, K9 = Socket RJ11 6/6, horizontal (Farnell # 9732071)
K10 = 2x5-way flat cable socket

K11, K13 = 2-way side entry male header, PCB plug-in connector, pitch 5.08mm (0.2”), male, soldered connection, 90° (Farnell # 9633197)
2-way female terminal block with screws, free plug, pitch 5.08mm (0.2”) (Farnell # 9633030)

K12 = DC adapter socket, 2.1 mm (0.83”), PCB mounting
K19 = 3-way polarized vertical header, wire-to-board, lead pitch 2.54mm (0.1”) (Farnell # 588581)
K21 = 6-way polarized vertical header, wire-to-board, lead pitch 2.54mm (0.1”) (Farnell # 588611)
K20 = Jack socket 3.5mm (0.14”), mono, PCB (Farnell # 152206)

M1 = P542-M481U-G17L82 (McLennan Servo Supplies), unipolar stepper motor, 2400 steps per revolution (not included in kit of parts)
S1 = push-button, tactile, SPNO
Y1 = Elektor ARMee board mk.II (with LPC2106/01 and 14.7456 MHz crystal)
SK 409/25,4 STS (Fischer Elektronik), heat sink for TO-220/TO-3P, 8.2°K/W (Farnell # 4621293)
IC socket, DIP8
12 jumpers, pitch 2.54mm (0.1”)
2 sockets 1x20-way, lead pitch 2.54mm (0.1”)
1 M3 screw, 10mm (0.4”) to secure heat sink
1 M3 nut to secure heat sink screw

PCB, ref # 080253-1

Outside the PCB:

K14, K16 = 2-way housing, wire-to-board (Farnell # 1098459)
K18 = 3-way housing, wire-to-board (Farnell # 1098438)
K22 = 6-way housing, wire-to-board (Farnell # 1098456)
R56, R57 = KTY81/210 (NXP), temperature sensor, positive temperature coefficient, SOD70 case

Board # 080253-2

R1 = 10kOhm, 0.25W, 5%
R2 = 4Ohm7, 1W, 5%

C1, C2, C4 = 100nF / 50V, ceramic, lead pitch 2.54mm (0.1”)
C3 = 47uF / 63V, Electrolytic radial, lead pitch 2.54mm (0.1”)

BZ1 = EMX-7T05SP, magnetic transducer, 5V, lead pitch 7.6mm (0.3”) (Farnell # 1193323)
D1, D2, D3 = 5V6, 0.5W, zener diode
IC1 = MCP23017, 16-bit I/O expander with I2C serial interface, DIP28 (Farnell # 1332088)
JP1, JP2, JP3 = 3-way pin header, lead pitch 2.54mm (0.1”)
K1 = RJ11socket 6/6, horizontal (Farnell # 9732071)
LCD1 = LCD Displaytech 204B, 4x20 alphanumeric
P1 = 10kOhm preset, PCB mounting
S1…S4 = 3FTL6 (Multimec), push-button, tactile, SPNO (Farnell # 1132885)
S5 = EC11B15242 (ALPS), rotary encoder, 5V, 15 PPR, panel mount, 11mm (0.44”) (Farnell # 1191733)
T1 = ZMX61P02F (Zetex), MOSFET P, SOT23 (Farnell # 9525297)
3 Jumpers, lead pitch 2.54mm (0.1”)
IC socket, DIP28 narrow
1x16 way socket, lead pitch 2.54mm (0.1”) (LCD connection)
AW 110/16-T (ASSMANN), 1x16 way pinheader, lead pitch 2.54mm (0.1”) (LCD connection)
4 MDLSP1-10M-01 (RICHCO), nylon locking post, height 10mm (0.39”) (Farnell # 1325985)
4 AQC09-24.2 (MULTIMEC), black cap for push-button, height 24.2mm (0.95”) (Farnell # 1132965)
7 self-tapping screw 4x1/4 to secure PCB to case
Case, model BS 800 F-7035 prod nr. 82800135 (BOPLA), light grey; 98x34x209 (WxHxL) [mm] (3.85x1.34x8.23) (WxHxL) [inch]
Black knob, 22mm (0.85”) diameter, 21mm (0.83”) height, 6mm (0.24”) shaft diameter
6-pole RJ11 Male to Male Modular Cable (1m) (3’) to connect 080253-1 to 080253-2
PCB ref. # 080253-2

090146-91 Elektor ARMee board mk.II

LPC2106FBD48/01 (NXP), 32-bit ARM microcontroller; 128 KB ISP/IAP flash with 64 KB RAM, LQFP48
14.7456MHz quartz crystal, HC49/US case, low profile (Farnell # 1538745)
The other components on this board remain unchanged

PCB, Elektor order code 090146-91
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