Help (Pro mini with Adafruit servo controller on one PCB)

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darkdarts
Posts: 3
Joined: Mon Jun 27, 2016 6:07 pm

Help (Pro mini with Adafruit servo controller on one PCB)

Post by darkdarts » Mon Jun 27, 2016 11:06 pm

Recently I have been trying combine the pro mini by Spark fun and the adafruit on to a single PCB. I downloaded the schematics from the Sparkfun and adafruit websites and combined them. I was wondering If you could help me check my schematics.


Schematic image here: https://goo.gl/photos/v7ZBqen32RKabRSc6

davep238
Posts: 157
Joined: Thu Dec 13, 2007 8:51 am
Location: Burke, VA, USA

Re: Help (Pro mini with Adafruit servo controller on one PCB

Post by davep238 » Sat Jul 02, 2016 8:30 am

1) the schematic is messy, especially with angled and stair-step lines. Use straight lines when possible.
2) you do need the "this vs that" bypass caps. I don't see the need to put them into a box.
3) get rid of the 2 buses and just connect the wires together. Name the nets "SDA" and "SCL" vs "B$1" and "B$2".
4) move the bypass cap near the PWM chip to the left because it overlaps the SDA wire at the PWM chip.
5) the reverse polarity MOSFET should be near the voltage regulator.
6) what's the value of C7?
7) if power comes into the board via a connector, then the connector needs to be shown. otherwise I assume that the wires from the power source are soldered to the board.
8) the IMU connector should have a ground pin vs having a separate ground connector.
9) why are the PWM12 and PWM13 connectors separate from the other PWM connectors?
-Dave Pollum
programmer / digital designer
PCBs designed for low cost

darkdarts
Posts: 3
Joined: Mon Jun 27, 2016 6:07 pm

Re: Help (Pro mini with Adafruit servo controller on one PCB

Post by darkdarts » Fri Jul 08, 2016 12:28 am

Hey Davep238,

Thanks for the reply.

Yes schematics are a bit messy, yet to tidy it up.

For the this vs that, was because the caps seemed to be used as a protection circuit for the ICs, and I was wondering If I could just use one instead of two

quick question the "5) the reverse polarity MOSFET should be near the voltage regulator." do you mean the location of the voltage regulator or?

C7 depends on no. of motors used(exactly the same as the ada fruit servo board)

The input power pins are at the top left

The pin for the IMU ground is not seperate, just could not find a 4 pin layout

PWM 12 and 13, just place there, no reason

davep238
Posts: 157
Joined: Thu Dec 13, 2007 8:51 am
Location: Burke, VA, USA

Re: Help (Pro mini with Adafruit servo controller on one PCB

Post by davep238 » Fri Jul 08, 2016 6:39 am

The caps are not "protection circuit". They are bypass caps (google them). They are mandatory and must be located near the power pin of each chip on the PCB.
When looking at the voltage regulator on the schematic, it took me a while to notice that the MOSFET was part of the power supply. I think the MOSFET should be near the voltage regulator in both the schematic and the PCB to avoid any more confusion. It's not obvious how the MOSFET fits into the circuit. It seems to me that the MOSFET should go between the "RAW" point of the regulator and the switch.
If you can not find a 4-pin connector, you can always create one, by expanding a 3-pin connector. Creating library parts is not difficult and everyone needs to be able to create new parts.
-Dave Pollum
programmer / digital designer
PCBs designed for low cost

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