I hoped to create circuit that controlled a motor via a PWM speed controller, which in turn is also controlled via a digital pentiometer (MCP4131)
The LCD is driven by a I2C serial interface board.
I ran the parts and sketches separately and successfully. But when I came to tie it all together the Arduino Pro Mini no longer powers up from an external source, only USB via a FTDI breakout board.
Any tips on where I may have gone wrong would be greatly appreciated. Please let me know if you require more information.
Hard to say but, as wired in the diagram, it appears that the motor may have caused an inductive kickback into the on-board voltage regulator? It is best not to power motors and Arduino from the same power supply.
Yeah - that's my guess... I'll bet he disconnected the battery while the motor was spinning and the voltage spike resulted in the damage.
A diode across the motor terminals (with the band towards the + side) would prevent that from causing damage in the future. A cap between power and ground would be a good idea too.
(edit - sorry, I wrote battery when I meant motor)
In your diagram, you have the motor wired directly to the battery so it will run all of the time, three leads of the digital pot connected to nothing, and no visible DC motor controller.
An accurate representation of your whole circuit in the form of a properly-labelled schematic diagram would be much better. Fritzing is crap, and leads to too many mistakes.
Edit: And I got the same impression as DrAzzy if your circuit really is wired as shown. The moment the battery is disconnected, the motor's EMF powers everything.
Thank you for all your advice so far. Apologies, you're right, I should've shown the motor wired via the PWM speed controller! (I was in a rush to post my issue before heading to bed.) The speed controller is powered from the same battery though. The 3 loose wires from the digital pot are connected to the SC also.
I like/understand the idea of having a diode to prevent the 'kickback' you mentioned - Thanks.
I shall get on to the schematic diagram tonight - any recommendations on an alternative for Fritzing? Happy to Google it though.
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