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Author Topic: Do you notice any issues with my circuit?  (Read 854 times)

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Offline MastermimeTopic starter

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Do you notice any issues with my circuit?
« on: September 14, 2012, 09:57:26 PM »
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

« Last Edit: September 15, 2012, 09:18:54 AM by Mastermime »

Offline waltr

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Re: Do you notice any issues with my circuit?
« Reply #1 on: September 15, 2012, 12:39:30 PM »
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.

Offline MastermimeTopic starter

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Re: Do you notice any issues with my circuit?
« Reply #2 on: September 15, 2012, 08:47:31 PM »
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.

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.

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.
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.
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

Offline Soeren

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Re: Do you notice any issues with my circuit?
« Reply #3 on: September 16, 2012, 05:34:31 AM »


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


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?
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.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline MastermimeTopic starter

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Re: Do you notice any issues with my circuit?
« Reply #4 on: September 16, 2012, 06:13:41 PM »
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.

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


Offline Admin

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Re: Do you notice any issues with my circuit?
« Reply #5 on: November 11, 2012, 08:28:23 AM »
Quote
3- Is the + on the XBee from an Axon port pin? or a 3.3V regulator.
It's fron an Axon port pin.  I forgot to mention that Xbee is connected to a development board.

The Axon 3.3V output can only supply up to 70mA. How much current does your Xbee need? If you overdraw the current, you might end up frying the USB on your Axon.

Offline MastermimeTopic starter

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Re: Do you notice any issues with my circuit?
« Reply #6 on: November 11, 2012, 10:42:58 AM »
I'm using this board so I figured I can supply it using the 5v LDO regulator
http://adafruit.com/products/126

 


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