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Topic: MOSFET or BJT for data lines? (Read 644 times) previous topic - next topic

sarah20

Hi,
Have you prototyped any of this, before committing to PCB, like connecting the Tx/Rx to the controller to see if you can communicate with it.
It looks like you are trying to make a OBDII reader.

Tom... 
i have free access to a reflow oven and solder paste and the pcb costs only like 2 bucks so why not just making the pcb right of the bat! i have tested different parts of the circuit but unfortunately its hard for me to test the whole schematic before fully assembling it as STN only comes in pain in the *** package!
yes im trying to make a OBDII reader in a tiny seamless pcb so i can just attach it to my car and basically forget that its there! i just got a new car and i want to add a bunch of random features to it and making my own OBDII reader is a better option than buying a bulky one from sparkfun.
thank you for all your help tho!

sarah20

Not posting the whole schematic severely limits the help you will get, we are not telepathic (well, I'm not) and can only comment on what we can see. However, what I can see is the MOSFETs across Rx and Tx, regardless of whatever else I can or can't see, this won't do anything useful.

I see 6v6gt suggested DIP switches, if that does what you want then all good. I have zillions of 4052s and would be happy to send you some if you are in the UK.
fully noted!
i have replaced the mosfets with dip switch as it is a simpler and better solution. thank you for you offer but im in Canada.

TomGeorge

#17
Oct 11, 2020, 01:59 am Last Edit: Oct 11, 2020, 02:00 am by TomGeorge
i have free access to a reflow oven and solder paste and the pcb costs only like 2 bucks so why not just making the pcb right of the bat! i have tested different parts of the circuit but unfortunately its hard for me to test the whole schematic before fully assembling it as STN only comes in pain in the *** package!
yes im trying to make a OBDII reader in a tiny seamless pcb so i can just attach it to my car and basically forget that its there! i just got a new car and i want to add a bunch of random features to it and making my own OBDII reader is a better option than buying a bulky one from sparkfun.
thank you for all your help tho!
Okay, but don't forget to add test points and some indicator LEDs to help you trouble shoot your PCB, as this is prototype forget about making it a small as possible for the moment.

Make it so your major signal and power points can be easily accessed with test equipment.

Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

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