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MGV81 interface for 4 servo motors.


By Peter Giling

Latest news..............

The new interface MGV136 is available, as factory processed board.

Also for MGV81 and MGV81 with feed-back the initialisation program is applicable.

It makes it possible to adjust left an right angle of the servo, the running speed, and relay position.

This is all done while the MGV81 remains connected as usual to MGV50.

No extra connection or anything is to be made. Only new firmware needs to be programmed in PIC chip.

Jumper will be without function after installing the new firmware.

Implementation of this freeware is in Rocrail implemented.


The MGV81 is a simple Servo driver for 4 servo's,

It features 4 imputs max 20 volt to change position of servo between 45 and 135 degrees.

It can directly be connected to MGV50, or other function decoders.

Opto couplers provide electrical isolation between servo's and Loconet.

Additional supply 9 Vac or 12Vdc is to be connected to MGV81.

Higher voltage like 16V ac from train transformer, or booster power is also possible but VR1 needs extra cooling in that situation.

A small piece of alumimium , fixed with the same two fastening bolts of the voltage regulators, will usually do fine.

This version is designed as single side board.

This board is a D.I.Y. project. No boards available.

MGV81 V1.2 with feed-back

Rocrail includes the option for feed-back inputs. The MGV81 V1.2 is extended with this feed-back possibility and speed selection. On board is one speed selector.: all motors change position in 1 second, or all motors change position in 5 seconds. With this longer time, it is possible that a train already runs in direction of the turnout, before the turnout has come to a complete stop. Any other time is also possible by changing small settings in software of processor.

Therefore, a feed-back is important. Rocrail if properly set, will wait until feed-back confirms the turnout position. Because this will make it necessary to connect 4 in and 4 outputs to the MGV50, and standard header connector is used for connection to MGV50.

Picture of MGV81 V1.0 no feed-back

No further support on this board

Picture of MGV81 V1.2 with feed-back

Firmware for Processor PIC16F62X(a)

The program for the standard version of MGV81 is written in basic.

There is no need for high skill of programming, so a simple and really fast Basic compiler is used to achieve good results.

The compiler, used here, is called Pic Simulator IDE and can be downloaded from

Firmware for Processor PIC16F648(a)

The latest version of software in MGV81 is written C++ by Ewout Prangsma.

This version enables initialisation with The LocoNetToolbox

Connection old version to MGV50

5 screw terminals are used to connect the interface to MGV50.

Terminal 1-4 are the to be connected to 4 of the 16 I/O terminals on MGV50.

Terminal 5 is to be connected to - Point on MGV50 terminals. (Pt 17).

Connection Version 1.2 to MGV50 (J6)

Bill of materials MGV81

Quantity Reference Part
4 R1 .. R4 1K
4 R5 .. R8 270E
1 R9 10K
1 RP1 4 x 10 K array SIL5
1 C1 ELCO 1000uF 25V radial
2 C2,C3 ELCO 10 uF 35V radial
1 C4 100 nF
1 U1 LTV844
1 U2 16F627/-628/-648
2 VR1,VR2 7805 TO-220
4 J1..J4 PSS 254/3G (Reichelt)
1 J5 AKL012-02 (Reichelt)
1 J6 AKL012-03 + AKL012-02 (Reichelt)
1 F1 Fuse PFRA 110
1 GR1 B80C1500 round

Bill of materials MGV81 V1.2

Quantity Reference Part
4 R1 .. R4 1K
4 R5 .. R8 270E
4 R9 .. R12 3K3
4 R13 .. R16 470E
4 R17 .. R20 270E
4 R21 .. R22 1K
4 R23 10K
1 C1 ELCO 1000uF 35V radial
2 C2,C3 ELCO 10 uF 35V radial
1 C4 100 nF
1 U1,U3 LTV847
1 U2 16F627/-628/-648 (A)
2 VR1,VR2 7805 TO-220
4 J1..J4 PSS 254/3G (Reichelt)
1 J5 AKL012-02 (Reichelt)
1 J6 PSS254/10G (Reichelt)
1 F1 Multifuse PFRA 110
1 GR1 B80C1500 round
1 Led1 Led 3mm red
1 Led2 Led 3mm green

Schematics and PCB drawings

The LocoNetToolBox

mgv81-en.txt · Last modified: 2018/11/12 08:56 (external edit)