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I am working on a project and I am needing someone with circiut board design experience. I have a circiut I have put together in expressPCB and need someone to go over it and make it perfect. Let me know if you can help me out. It's worth a few dollars for the job. SNO
Well here is the first phase completed. I am sure there are a few do's and dont's here but I feel pretty good being my first attempt at board design. The goal of this project is to incorporate a few off the shelf items into 1 box and have the option of connecting to a dumb unit, or a PC either via 1 usb cable or multiple serial cables or a combo of both. This box will be around 5x4x1.5 inches and will include OBD2 using the obd200 chip, Phidget 1010 8/8/8 controller, TPMS 433mhz reciever and GPS with external antenna. The GPS unit has ftdi usb/serial/bluetooth. I will be needing about 65 to start with so it should get costs down if anyone might have an interest in a product like this. SNO Attachment 68267
I'm no pcb expert, but would'nt you want to make all those individual grounds be solid copper instead of traces? My electronics design was in the mid 70's, but they taught us to keep as much copper solid as possible on ground.
If you look at the tips page for the software you are using there are some decent tips there for you.
And rray's suggestion is in there too..
Since I am looking to do something similar I would love to hear about your experience.
How big is your board?
I will likely go a different route, bread boarding things first to see if they work and going from there.
Although using "chips" such as the ODB200 and PHIDGET 1010 will save a lot of time.
Also, you may want to consider in circuit fuses or optical isolation for the inputs and outputs. Unless you are going to make your PHIDGET socketed so it can be replaced.
Unless they are for specific objects or are fused/isolated elsewhere people WILL hook those to things you don't expect and will blow them...
Ps, I am a newbie too but have had some "interesting" experiences in the past as I was one of those people that tried to hook up things the designer didn't expect and blew parts up.. ;) Luckily those designers put in circuit fuses that looked like resisters and I was OK... Swapped out a $.02 fuse and was on my way..
Thanks for the tips guy's. I should sort of clarify a few things, rray you are correct in having the grounds together. I blame it on my limited knowledge of the design app, but it will be a more unified mass of ground not traces of grounds in the final product. Board size will be 4.5x3.25 inches. This is the bottom board of a 2 board set. The top board will attach on to the bottom and will include the fuses/resistors/caps/led's as needed. I am working on the top board now. SNO
I was a PCB designer man in my last job !
What do you need to do exactly ?
First thing i see into your pcb that you use wires the GROUND and not a shape GROUND and that is a very bad thing !!!!
Second thing would be to add capacitors between the 5V and the ground for the ODB and PHIDGET chips (47nF/16v and perhaps a 1uf/16v)!!!
SNO; Take a look here at samples for how to design a proper input circuit for the phidget chip: http://www.phidgets.com/docs/Digital_Input_Primer
It might be wise as stated above to include some kind of design that will allow for some abuse by the user. A mosfet/transistor or a fully isolated input is to be preferred.
Thanks for all the suggestions. I realized my limitations and had a pro finish it off. It's now 4 layer with good planes in the middle. Everything is working perfectly on the board but a couple of small mods need to be done on the next version (diode holes too small, 1 analog input not inline with rest) as well as the 433mhz circuit will be replaced with something alittle more user friendly. It also now has a built-in self powered 4 port hub based on the gl850g chip.
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data from simulator reporting nicely
Attachment 68811
Very better with ground shape no ?
