Alas, it’s only for power. The data lines aren’t connected.
Wouldn’t be too hard to cobble (not the disastrous bot) one up from a spare cable
I think it wouldn’t hurt to have this option available, perhaps a simple solder pad jumper would be enough. Now in the early stages it seems to be a welcome option. In the future, once all safety issues are under control then it might be better again to get rid of it again due to the safety issues that come with having that jumper.
@bar I also wonder about the effect of noise on the H-bridge driver itself. I’m tinkering in Fritzing to draw a H-bridge PCB to get an idea what that is like. And to have a first rough prototype ‘bridged’ H-Bridge.
One full chip for each axis, so that gives 4 Amperes of available current per axis (that is, if the PSU can deliver that much power) But this would make it possible to load the H-bridges a bit more, make it more easy to mount a slab of aluminium.
It’s not fully clear to me how the sensing resistors do their thing. Does the L298 have it’s own protection on board? (the data sheet doesn’t mention anything). So that sussets that we need to measure the voltage across the 0.5 Ohm sensing resistor, Could we use the arduino for this? (would need 3 analog inputs) If current becomes to high then limit the machines speed. … But working to slow might cause the milling bit to heat up??? That could then become an issue right?
I’m still trying to get my head around all this…
This would provide an alternative power supply for the Arduino, but it wouldn’t change the issue in the original post. On the Arduino, if power is available from a source other than the USB, it will be used. If no other power is available, though, the USB power is used. As in the original post, loss of the 12V supply that leaves the host computer running would leave the Mega still running and waiting for the motors to move.
To circumvent that one would need to make a serial connection directly to the TX and RX pins of the Mega and leave the USB connection open. That would defeat the automatic reset and complicate uploading new firmware.
Powering from the motor supply would make running ‘offline’ possible though, if a way cut from a file stored on board were implemented 
.
1 Like