critique my board design - Page 1
Forum section: electronics / projects

author: jmctech
author_rank: Contributor
timestamp: January 21, 2015, 03:19:22 am
content: I am designing a control board for a kids power wheel ride on. I am using an ATMEG328P as the microcontroller. It is going to interface with a 2.4 ghz RC receiver. It will give a parent of a disabled child the ability to control the vehicle or with the flip of a switch on the remote the child will be able to drive it. I am relatively new to the board design. I have put in flyback diodes where the relays for direction and throttle are going to plug into the board. Any input will be greatly appreciated.

author: generic_username
author_rank: Regular Contributor
timestamp: January 21, 2015, 09:19:09 am
content: Just my 2 centsBoard looks ok, Only thing I can see atm is: you can certainly shorten some circuit paths as some of them seem kinda long, the think line from Gas Ped to Receiver has a 90° angle which is totally fine but doesn't match the rest of your 45° angles. And lastly you could if you need the space make the board smaller as there's not on it part wise.cheers.

author: void_error
author_rank: Frequent Contributor
timestamp: January 21, 2015, 09:50:55 am
content: You can easily make that half its current size...

author: okaresz
author_rank: Newbie
timestamp: January 21, 2015, 05:44:32 pm
content: I suggest wider clearance between your ground plane and the other traces. Especially around the TH pads. With this small gap around the pads on a poor quality / home manufactured PCB, chances are you will create some shorts when soldering.And also around screw holes.

author: ajb
author_rank: Super Contributor
timestamp: January 21, 2015, 06:28:55 pm
content: - Your reset network is wrong. ATMegas need a resistor pulling reset up to Vcc, and optionally a cap from reset to ground.- You need decoupling at the MCU. 100nF or so, one at each Vcc pin, as close as possible.- D7 could be problematic. Vcc is connected to the ISP header so that the programmer can detect the target MCU's operating voltage and set its IO levels (it may actually power the target side of the IO level shifters in some programmers--not sure). D7 will prevent that, so will prevent at least Atmel's tools from entering programming mode. Third party tools may not care, especially cheap ones. If your programmer will be supplying target power while programming, then D7 is fine.- How much current are you planning to switch with those transistors?-Your ground plane is pretty carved up. Consider spreading the legs of your diodes to allow the ground plane to flow more freely. Also consider orienting the diodes (and maybe some wire links) vertically and preferentially route traces horizontally (or vice versa) to provide a more contiguous ground pour.

author: ajb
author_rank: Super Contributor
timestamp: January 21, 2015, 06:36:15 pm
content: You have a connector labeled "steer_pot", as in potentiometer? If so you probably want to route that to one of the ADC channels on Port C.

author: jmctech
author_rank: Contributor
timestamp: January 23, 2015, 01:00:49 am
content: Thank you for all the help, I am making some changes based on your replies. I do have a question though, if was to go with solid state relays over standard relays would I still need flybacks in place?