Connecting Hardware To Axon II

[Mastermime]

Hello everyone,

I have a couple questions about connecting hardware to the Axon II.  Here is my information.

Voltage supplied to the Axon II: 12v
Wireless Transmission System: Xbee Pro XSC

One XSC will be connected to the Axon II.  Another XSC will be connected to a laptop.  Should I use packetized serial or simple serial? 

Do I connect the Sabertooth signal wires to UART? Tx Rx?
Where should I connect a HS-65 mg servo?  5v regulated with the signal wire connected to hardware pwn pin?
The XSC also connects to UART, right?

Thanks

[Admin]

Voltage supplied to the Axon II: 12v
Wireless Transmission System: Xbee Pro XSC

How will your Xbee be powered? (they fry above 3.6V . . . although it has 5V tolerant UART inputs which is good)

One XSC will be connected to the Axon II.  Another XSC will be connected to a laptop.  Should I use packetized serial or simple serial?

Simple serial will be best to start off with . . .

Do I connect the Sabertooth signal wires to UART? Tx Rx?

Axon Tx connects to Sabertooth Rx. You won't need to use the Axon Rx.

Where should I connect a HS-65 mg servo?  5v regulated with the signal wire connected to hardware pwn pin?

Servos fry with voltages above 6V. You could attach the servo the regulated power bus, but it can only handle up to 2A. Your servo is likely to drain about 1A. The regulator is burning away 12V to 5V at that 1A and so it may or may not cause over heating issues.

Your better choice is to use a 6V battery and power your servo(s) through the unregulated bus.

The XSC also connects to UART, right?

yeap


A quick reminder: always connect the grounds of all your devices together. It's a common beginner mistake


Also, if you haven't already bought the Axon II and Xbees, I'd like to point you towards this much cheaper and easier to use product:
http://www.societyofrobots.com/axon_mote/
It's basically an Axon with built-in Zigbee wireless modules.

Here is an example of Axon Motes being used with a Sabertooth motor driver and a servo:

Wireless Robot w/ Axon Mote

[Mastermime]

How will your Xbee be powered? (they fry above 3.6V . . . although it has 5V tolerant UART inputs which is good)

I was planning to use the 3.3v pins on the Axon II.

Simple serial will be best to start off with . . .

Ok what are the benefits and drawbacks of using simple serial vs packetized serial?

Servos fry with voltages above 6V. You could attach the servo the regulated power bus, but it can only handle up to 2A. Your servo is likely to drain about 1A. The regulator is burning away 12V to 5V at that 1A and so it may or may not cause over heating issues.

Your better choice is to use a 6V battery and power your servo(s) through the unregulated bus.

Could I use a voltage divider or step down regulator to cut the 12v in half so I'd have 6 volts?  Then I could just connect it to the unregulated bus.  Any reasons why this would be an issue?

A quick reminder: always connect the grounds of all your devices together. It's a common beginner mistake

As opposed to...?  I dont know if I understand you correctly.  Wouldn't the circuit not run properly if the grounds weren't connected to each other?

Also, if you haven't already bought the Axon II and Xbees, I'd like to point you towards this much cheaper and easier to use product:
http://www.societyofrobots.com/axon_mote/
It's basically an Axon with built-in Zigbee wireless modules.

I have purchased all my electronics already.  The reason why I didn't use the axon mote is because I need the long distance wireless transmission system the XSC offers.

Thanks for the help!  I truly appreciate it!

[Admin]

I was planning to use the 3.3v pins on the Axon II.

uhhhhh no. lol

The Axon 3.3V output can only supply about ~73mA. The Xbee requires 265mA. You'll fry your Axon USB port if you tried that.

You will need to use a separate 3.3V regulator that can handle at least 1W of power and 0.3A.

Ok what are the benefits and drawbacks of using simple serial vs packetized serial?

This is in reference to the Xbee, right? The word 'simple' doesn't appear in it's datasheet . . . where do you see it at? Packetized means your code will need to process it as packets, vs simple where you don't need that extra processing effort.

Could I use a voltage divider or step down regulator to cut the 12v in half so I'd have 6 volts?  Then I could just connect it to the unregulated bus.  Any reasons why this would be an issue?

If you absolutely must have 12V, then you should use a switching regulator that can handle the current you need. Here is a list:
http://www.societyofrobots.com/robotforum/index.php?topic=11559.0

Wouldn't the circuit not run properly if the grounds weren't connected to each other?

You'd be amazed at how many people don't connect their grounds together, and then get confused why it's not working

For example they'd have an Axon with one battery, and a Xbee with another battery, and then connect the Rx/Tx lines for communication. They assume grounds are connected to the batteries so it's ok. But they don't realize grounds must be common, ie ground of one battery connected to ground of the other.

I have purchased all my electronics already.  The reason why I didn't use the axon mote is because I need the long distance wireless transmission system the XSC offers.

You're right, I just realized it promises 3x the range of the Mote . . .

[Mastermime]

uhhhhh no. lol

The Axon 3.3V output can only supply about ~73mA. The Xbee requires 265mA. You'll fry your Axon USB port if you tried that.

You will need to use a separate 3.3V regulator that can handle at least 1W of power and 0.3A.

Oh haha.  Sorry for my ignorance.  I'm pretty new to MCUs.  I'm going to power it using a separate 3.3 regulator. http://www.ebay.com/itm/120828011259?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_10924wt_940

This is in reference to the Xbee, right? The word 'simple' doesn't appear in it's datasheet . . . where do you see it at? Packetized means your code will need to process it as packets, vs simple where you don't need that extra processing effort.

Oh I'm a little confused right now.  You told me to start off with simple serial.  I am also new to serial control.  As you may have predicted, this project is a bit of a learning experience for me.  Yeah as I am looking at the datasheet it seems as if the only available option is to use packetized serial.  Were you saying earlier that I should start out with using simple serial and then do the extra processing later?  That'd screw up all my baud rates, wouldn't it?

If you absolutely must have 12V, then you should use a switching regulator that can handle the current you need. Here is a list:
http://www.societyofrobots.com/robotforum/index.php?topic=11559.0

I'm afraid I do need the 12v because I have a CCTV camera circuit that requires 12v.  Now that I think about, I am only having another temp. sensor on the 5v regulated power bus.  I have a cooling system also so I don't think overheating would be an issue.  I just have to connect the signal wire on the servo to a hardware pwm pin on the unregulated section of header pins because there aren't any on the 5v section, right?

[Admin]

Nothing wrong with packetized serial, it's just extra programming effort on your part. You'll have to read through the datasheet to figure out exactly how to decode everything.

I just have to connect the signal wire on the servo to a hardware pwm pin on the unregulated section of header pins because there aren't any on the 5v section, right?

yeap

[Soeren]

Hi,

I'm afraid I do need the 12v because I have a CCTV camera circuit that requires 12v.

The CCTV-cam may be able to run on 5V (or perhaps 9V). If you open it and look for a voltage regulator, the numbers on that would help you find its output voltage and this regulator can usually be bypassed if the voltage is regulated already.

[Mastermime]

The CCTV-cam may be able to run on 5V (or perhaps 9V). If you open it and look for a voltage regulator, the numbers on that would help you find its output voltage and this regulator can usually be bypassed if the voltage is regulated already.

That seems a lot more difficult than connecting a regulator inbetween the 12v pins and the servo.  Also wouldn't screw up the transmitter?

[Soeren]

Hi,

That seems a lot more difficult than connecting a regulator inbetween the 12v pins and the servo. 

Sure... And buying a 'bot is even easier.

Also wouldn't screw up the transmitter?

You mentioned a CCTV cam and they don't include any transmitters ( (per definition - Closed Circuit TeleVision). Adding a transmitter takes it out of the CCTV definition.

Sounds more like a wireless security cam you have then and yes, the transmitter may (or may not) need a higher voltage.
Anyway, it was just meant as a help to reduce your power requirements, but do whatever you like

[Admin]

If you're using a wireless security cam, you can use a small rechargeable 9V lithium battery for it. Then you can use a separate 6V NiMH battery pack for the rest of your robot.


It's just when you have 12V, and you use a regulator to bring that voltage down to 6V, you're literally burning away half the battery charge as wasted heat. Even with a switching regulator, you're burning a good 10-20% of your battery away for nothing. Your robot then must carry a battery that's 2x bigger/heavier than it needs to be.

What Soeren suggests is pretty easy to do, and shouldn't take you more than about 15 minutes of effort.

[Mastermime]

If you're using a wireless security cam, you can use a small rechargeable 9V lithium battery for it. Then you can use a separate 6V NiMH battery pack for the rest of your robot.

I can't do this because my motors require 24 volts and I have a bunch of other components that require 12v.  I have to use SLA batteries too for the runtime I need (1.5- 2 hours). 

I'm just going to regulate the 12v on the axon II down to 5v using a LM7805 regulator.

[Gertlex]

For the xbee, I'd recommend these two boards (one is for computer, one is for your bot).  They take care of the regulated voltage for you, and the latter connects easily to your axon's UART once you put some wires on it.

http://www.trossenrobotics.com/p/uartsbee
http://www.trossenrobotics.com/store/p/5977-XBee-Explorer-Regulated.aspx

[Mastermime]

Oh sorry guys

[Resilient]

Mastermime just PMed me. Apparently he is having technical difficulties. I guess he was trying to modify a post and couldn't and tried to post a new one but got an error.   

So he still cares. Just cant seem to post.

[Mastermime]

Mastermime just PMed me. Apparently he is having technical difficulties. I guess he was trying to modify a post and couldn't and tried to post a new one but got an error.   

So he still cares. Just cant seem to post.

Thank you so much for the help.  I just posted on a new server.  something is wrong with my server at home    I kept getting an error when trying to post.

Here was what I was trying to post:

Oh sorry guys I forgot to say that I purchased the Xbee XSC Development Kit.  This includes a development board that looks like this so I think I'm all set for UART and transmission.
http://microframework