PF Motor Power

[SillyOldfart]

Hi; I am new to Eurobricks Forum, having been a member of the Lego Forum which doesn't seem to be on-line anymore, so I'll charge straight in.

Does anyone know anything about the amperage required to drive an 8883 motor?

I dreamed up a special 8871 extension cable with a flip-flop relay inserted such that power to the motor could be reversed by two microswitches - one at each end of a short track. The idea was that a bogie (ie, railway truck) would be driven one way by the motor until it hit the microswitch at the end of the track, then be automatically reversed until it hit the microswitch at the other end, and so on back and forward. The two outer wires (+9v and 0v) carry straight through. The two inner wires are switched between each other by the (heavy duty) relay, with power supplied by the +9v line, to alternate motor direction. 

The relay works and the correct voltages are evident at the appropriate (light grey) socket terminals, but there is absolutely no movement by the motor. (The motor runs perfectly without the extension cable.) 

The wiring I used is the same as in the cable, but do I have a current problem, or do the four wires actually do something very different from +9V - +9v rotate clockwise - +9v rotate anticlockwise - 0v??. 

 

Edited January 24, 2018 by SillyOldfart

[technic_addict]

16 minutes ago, SillyOldfart said:

Hi; I am new to Eurobricks Forum, having been a member of the Lego Forum which doesn't seem to be on-line anymore, so I'll charge straight in.

Does anyone know anything about the amperage required to drive an 8883 motor?

no load 65 mA

stalled 850 mA

[mahjqa]

All the motor info you'll ever need is here: http://www.philohome.com/motors/motorcomp.htm

[Rikus]

Why not use a PF pole reverser, together with a “mechanical” solution to operate it?

 

something like this:

 

Edited January 24, 2018 by Rikus
Added link

[SillyOldfart]

Yes, I did think about a pole-reverser, but the motor is on the track. There is no room for the motor (and certainly not the battery pack) on the bogie, mainly because the bucket tips.

[Andy D]

Hey @SillyOldfart if you are really a Silly Old Fart (over 50) you might want to check out the 

and request your "Older Than Dirt" badge of honor.

Welcome to EB. Good luck with your PF motor problem.

Andy D