schematic help

Other Hardware General Electronics
1

anybody feel like taking a look at this and giving me some pointers,Im still learning, I have tested most of it on breadboard but before I make an actual pcb just wanted some advice. my plan is to make a shield that will plug into my arduino mega and control a hotplate via ssr, ph, a magnetic stirrer, and a stepper motor for automated titration. like i said im still learning so by all means tell me if im messing up. thanks

labbuddy.png
labbuddy.png1036×822 26.4 KB

2

Am I correct that it is a single board? If so, it's hard to evaluate without knowing more about the external wiring and devices.

3

Looks like you have Vin going to the output of the regulator, if so, don't!
Don't see any decoupling.

4

Thanks for the replies. Yes its a single board. The ph and temp are shields so they should be fine as is my main concerns are with my values. Vin is the pin to power the arduino so that should be correct coming from the output of the regulator. What is your recomendations on decoupling .

5

If the voltage going out on your Vin pin is 5 volts, you should connect your regulator output to the Arduino +5 volt pin instead. That is if you want to power your Arduino from this cct.
.

6

Decoupling:
http://www.murata.com/~/media/webrenewal/support/library/catalog/products/emc/emifil/c39e.ashx

7

Ok. Thank you that is a much more in depth tutorial than ive been reading on decoupling I appreciate the help and information. Ill change the supply pin and work on my decoupling.

8

I'm having a hard time understanding why you would deliberately avoid using sense resistors RSA and RSB. (RSA = RSB = 0.5 ohms (P = R*I = 0.5 * 2A = 1W) . The whole point of using sense resistors with one end connected to ground is it makes it dead simple to monitor motor current using analog inputs. You're designing the board and you are deliberately leaving out a really useful feature (motor current feedback). In addition, your L298 has absolutely NO protection diodes (see schematic on page 8 of the L298 Datasheet) . You're designing a PCB and haven't even looked at the datasheet ? (shame on you)

1- add sense resistors
2- add protection diodes (1N4002 , 1N4003, or 1N4004) (1N4001 are marginal for a 2A motor current but would be better than no diodes)