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Do you notice any issues with my circuit?

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Mastermime:
Hello everyone,

Could one of you verify that my circuit will properly work?  I've done all the soldering and what not and now just have to program it.

A few things to add to the schematic that are in my circuit (didn't have room);  Diodes on both relays (coils), 1k resistors on MOSFETs, and an XLR port connected the battery terminals for charging. 

Also, I taught myself how to write schematics so I'm not sure I'm doing things the proper way so if I could get feedback on that too, that'd be great.

Thanks

waltr:
Schematic isn't bad for a first try.
A few things I noticed are:

1- No power return from the Sabertooth motor driver to the SLA batteries. You want this to go directly to the battery and not through the other circuits.

2- No current limiting on the LEDs. Usually a series resistor.

3- Is the + on the XBee from an Axon port pin? or a 3.3V regulator.

4- Is the Servo a RC hobby servo? If so then it needs a control wire.

The start programming you need to decide which Axon port pins will be used for each feature.

Mastermime:

--- Quote ---1- No power return from the Sabertooth motor driver to the SLA batteries. You want this to go directly to the battery and not through the other circuits.

--- End quote ---

Ok, so ground goes directly back to the battery?  And that is to prevent damage to the relay due to the regeneration feature on the Sabertooth, right?


--- Quote ---2- No current limiting on the LEDs. Usually a series resistor.

--- End quote ---

I thought that because the supply voltage is only 12 volts and the the total forward voltage drop will 13.2 volts, I won't need a resistor.  The LEDs will just be dimmer and that's fine.  Or do I still need a resistor?


--- Quote ---3- Is the + on the XBee from an Axon port pin? or a 3.3V regulator.

--- End quote ---
It's fron an Axon port pin.  I forgot to mention that Xbee is connected to a development board.


--- Quote ---4- Is the Servo a RC hobby servo? If so then it needs a control wire.

--- End quote ---
Yes, its the HS-645mg modified for continuous rotation.  That is in my circuit. I just forgot to put it in the schematic.

Thanks a lot for your input

Soeren:



--- Quote from: Mastermime on September 15, 2012, 08:47:31 PM ---Ok, so ground goes directly back to the battery?  And that is to prevent damage to the relay due to the regeneration feature on the Sabertooth, right?

--- End quote ---
No, it's to keep the motor current from influencing the rest of the circuitry.



--- Quote from: Mastermime on September 15, 2012, 08:47:31 PM ---I thought that because the supply voltage is only 12 volts and the the total forward voltage drop will 13.2 volts, I won't need a resistor.  The LEDs will just be dimmer and that's fine.  Or do I still need a resistor?

--- End quote ---
LEDs are current controlled devices!
LEDs have a very narrow voltage range (although some of the white ones do have a wider range than other colors). Under a certain voltage, they don't light at all and even a little too high and they're toast.
You need current limiting, so split them into two strings and add a resistor to each string.

Mastermime:

--- Quote ---LEDs are current controlled devices!
LEDs have a very narrow voltage range (although some of the white ones do have a wider range than other colors). Under a certain voltage, they don't light at all and even a little too high and they're toast.
You need current limiting, so split them into two strings and add a resistor to each string.
--- End quote ---

Ok thanks.  I'll add a 270 ohm resistor to each string.

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