About the article

Smooth Operator

for model railway turnouts and semaphores

Smooth Operator
In many model railway layouts, electromagnets instantly snatch turnouts and semaphores from one position to another with an associated ‘clunk’ noise. Armed with a PIC micro and a small servo, the circuit described in this article provides much slower, smoother, quieter and hence more realistic operation of these mechanical devices. There are a large number of model railway builders using proprietary track and points to realise their layouts. When adding remote controls for points (turnouts) there is often disappointment with the unrealistic and noisy movement of the mechanism. There are commercially available motorised units but these are expensive as well as difficult to install. A further disadvantage of commercial units is that the force they use is often detrimental to fine scale turnouts in that it can easily cause damage if not precisely adjusted and maintained.
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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
R1-R6 = 10kOhm
C1 = 100µF 25V radial
C2 = 10µF 16 V radial
C3 = 100nF
C4,C5 = 22pF
D1 = 1N4001
D2,D3 = 1N4148
T1 = BC547
IC1 = PIC16F84-10P, programmed, order code 030209-41
IC2 = 7805
JP1 = 2-way pinheader with jumper
K1 = 3-way pinheader
K2 = 3-way PCB terminal block, lead pitch 5mm
K3-K6 = 2-way PCB terminal block, lead pitch 5mm
S1,S2 = pushbutton with 1 make contact, e.g., type D6-R
X1 = 8MHz quartz crystal
RE1 = relay, PCB-mount, 12V SPDT, e.g., Siemens V23057
PCB, available through The PCBShop
Proton PIC Basic Plus source code, order code 030209-11 or Free Download
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