User Tools

Site Tools


GCA115 stand alone servo driver


By Peter Giling


H0 scenery can be much more than just trains.
Many people are very engenious in creating all kinds of funny and/or realistic little scenes around the model railroad.
One thing that is particularly difficilt for many, is to make a repating movement.
Those things are available on the market, but very often are running too high speed, or have no intervals etc.
GCA115 constists of a small microprocessor and three adjust potentiometers, to control a servomotor.
With these trimmers it is possible to adjust speed, maximum length of the movement and the interval between movements.
Any standard 5V servomotor will do. Look at Conrad catalogue for cheap options.
J3 provides an input to be able to start/stop the action, also connectable to the LocoIo GCA50.
So Rocrail could have something to say in it as well.

A jumper is provided to select between single or 2 way action.

So from now on, all kinds of movements are possible.

- Forklift in action…

- and garage doors opening and closing….

- and soldiers presenting their gun….

- and the towerbell is moving…

- and the moonwalk is working…

- and a man is digging in his garden…

- and a container truck loading or unloading…

- and women drinking their never ending coffie on a terrace…

- and the unexpected things that people do in their bathroom…

- not to mention the bedroom….SENSURED!..

And 1001 others…. Have fun!

The hardware

The schematics
The PCBoard + parts placement
N.B. Self made pc-boards are not supported!

Bill of materials

Qty Reference description
1 R1 270E
1 R2 2K2
2 R3,R4 10K
3 P1,P2,P3 Trimmer 75H10K
1 C1 ELCO 1000 uF 16V
1 C2 100 nF
1 C3 ELCO 10 uF 25V
1 Le1 LED 3mm
1 VR1 78L05 TO-92
1 VR2 7805 TO220
1 U1 PIC12F675 with socket
1 J1 PSS254/3G
2 J2,J3 AKL012/02
1 GR1 B80C1500 round
1 F1 FUSE 09.A MFR

Due to the fact that the servomotor can draw up to 0,5 A or more, it is advicable not to exceed 8 Vac or 12 Vdc as power supply.

If more is used, the 7805 TO220 chip needs additional cooling.

Also C1 needs to be adapted to the correct voltage.

Consider that i.e. 16 Vac for power in will result in approx 22 volt to C1.

The firmware

.hex file can be used directly to program Chip PIC12F675.

Program is build in basic with Pic Simulator IDE. Downloadable from

mgv115-en.txt · Last modified: 2018/11/12 08:56 by