Wireless Controlled Servos To Ez-b V4

 
#1

I have two servos which cannot be hard wired directly to the EZ-B controller. They will be located about 10 feet from the EZ-B and I can't run wires to them. These servos will be controlled by the script running in the EZ-B using information from the camera input. Can I use a wireless device like an xbee to connect the servos to the pwm outputs on the EZ-B? Has anyone ever tried this or has suggestions as to if it can work?

Ron

#2

No. Servos use a PWM speed that is far beyond the radio transmitting ability of xbee.

Here is how a servo works... it works in microseconds, not milliseconds.

#3

Thanks DJ. I forgot the speed of the data going to the servo was so fast. Is there any other way to you can think of to run these servos.

Ron

#4

How about a second EZB(4) located with the servos.

#5

I may have to go that way. I was trying to see if anyone has any ideas like maybe an arduino or other communications device that they have used that works. If not I will go the second ezb. I wanted to be able to keep all the control function in one controller and wireless the communication like the ezb does.

Thanks Robot-Doc,

Ron

#6

You could potentially use an arduino with a Bluetooth module, and then connect a BT module to one of the UARTs on the EZ-B. You would need to write an arduino sketch that receives serial commands from the EZ-B (via a script) and sends position commands to the servo. (I imagine you could also get an xbee device that accepts TTL commands. I haven't ever researched it).

Seems more complex than it is worth unless you are so tight on space that you need to use an arduino mini or something.

#7

I really would like to go further with this idea.

I have a mini somewhere. Maybe an xbee from the EZB to the mini with a straight through sketch to drive the servos. Analog in (PWM) to PWM out.

Can I use the digital output of the EZB directly into the xbee to send out and use an xbee as an input in the arduino? Drive the servo from the arduino? I might try it, but I don't want to screw up the EZB port. (Master - EZB / Slave - Arduino)
Two of my projects would use this concept.

Can anyone advise me?

Ron

#8

You would most likely need to use the digital output of the ez-b as a serial output using the ez-b sendserial command. One xbee unit would get serial commands from the ez-b. It would send the commands from the ez-b wirelessly to the other xbee unit. The second xbee unit would be connected to something like an arduino's RX pin. The arduino device would interpret the serial string from the ez-b and perform an operation on the servo. it could just as easily be a picaxe or some other micro controller that could look at a serial string and convert an ascii character or number into a pwm signal.

#9

I agree with Robert. On way a serial protocol will be fast enough to reliably send pwm directly, but sending a command that an arduino can interpret and then pwm should be relatively easy.

When I suggested UART I wasn't thinking about the fact you can send serial on any digital port. Only need UART if you want the arduino to communicate back to the EZ-B, for instance acknowledging receipt of a command.

Alan

#10

Thanks to you both, One way communication is all I would need. I will begin to gather the devices.

Ron