Daisychaining

OK, so you want to make a tank bot with multiple BMD-S wheels. You can easily crimp several connectors onto one cable so that all the wheels get the same control signals but there are a few things to beware of.

Firstly, each wheel can draw up to 1A of current when stalled, which is about the same as the current rating for ribbon cable, so if you plug ten wheels onto one cable and stall them all you are going to put 10 amps through a cable rated for only 1A. We are not suggesting that you shouldn’t do this, just that you shouldn’t be surprised if your cable starts to melt, or catches fire.

Chain-assembly-Instr4.jpg

Connectors can go either way up, just so long as the polarising tabs are all on the same side.

Chain-assembly-Instr22.jpg

When you put two wheels on the same cable you end up connecting their quadrature sensor outputs together. These outputs are protected by 1k resistors so although you won’t damage them, you won’t get any useful quadrature signals from the wheels.

A way around this is to cut the two sensor wires connecting the first wheel in the chain to the rest of the chain, now you sill get nice clean sensor signals from that wheel, but none from the others. The photo below shows a cable with the sensor wires cut – The connector on the far left would plug into the controller and the middle connector would plug into the wheel from which the sensor signals would be read.

cutcable.jpg

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