Yes, exactly. The P2 needs around 200mA at 1.8V and a few mA at 3.3V. So if I use a switch mode regulator for the 1.8V most of the problem is solved. That would cut the total current draw on the 5V line to half.
My 50m test cable was AWG26 (0.15mm²). 2x50m has ~12 ohm. This causes a voltage drop of 2.4V at 200mA which is far too much. The real servo cable will have 0.5mm² (AWG 20) and 30m max. length or only 2.1 ohm max. resistance (+2 ohms for the filter inductors). This is still close to the edge at 200mA but no problem with 0.1A current draw and the switcher solution.
Comments
Really nice, ManAtWork!
Can you not get enough current across the cable and still have sufficient voltage on the far end to run the P2?
Could you use a switcher to get the 3.3V you need?
Yes, exactly. The P2 needs around 200mA at 1.8V and a few mA at 3.3V. So if I use a switch mode regulator for the 1.8V most of the problem is solved. That would cut the total current draw on the 5V line to half.
My 50m test cable was AWG26 (0.15mm²). 2x50m has ~12 ohm. This causes a voltage drop of 2.4V at 200mA which is far too much. The real servo cable will have 0.5mm² (AWG 20) and 30m max. length or only 2.1 ohm max. resistance (+2 ohms for the filter inductors). This is still close to the edge at 200mA but no problem with 0.1A current draw and the switcher solution.