I see a number of people here using multiple EZ-B on their robots, if the reason is just running out of port lines and number of servos etc, then there is a really good alternative.
Many moons ago, long before the dawning of the EZ-B, the first AIMEC:3 used the SD20 (I2C 20 channel servo driver) chip
Using the SD20 requires only 2 port lines of the EZ-B (I2C bus) to control up to 20 servos!
Another big advantage is that the SD20 handles all the servo control overhead, so not only does it release a lot of EZ-B port lines for sensors etc, it also releases the EZ-B from having to generate all the necessary PWM pulses. With the SD20 the EZ-B only has to send one servo position command across the I2C bus and then the SD20 does the rest.
At around 6.50 per chip (and resonator), its quite a low cost alternative, also the same company do ready built servo control module boards.
Hope this is of help.
Dave, I know you have been using multiple EZ-B on your B9, if you want to try out the SD20 then I have a spare that I can send over in your Bosh servo package, let me know if you want me to add it?
Upgrade to ARC Pro
Unleash your creativity with the power of easy robot programming using Synthiam ARC Pro
I presume (possibly wrongly?) that these expander boards are not fit for sensors such as the ultra sonic ping sensors that require 2 ports though? But for servo positioning and controlling of LEDs, TIP transistor circuits etc. though these look to be ideal, you may have just sparked my interest in progressing on Jarvis again - thank you for that!
I guess now I need to revisit the other topic where the SD boards were mentioned and correct myself a little
So I guess what I am trying to say is that if you have multiple servos hogging your EZ-B resources, then this I2C option is really neat!
adafruit 16 channel I2C servo controller... (better data on it here)
Devantech SD21 servo controller
Devantech SD21 is the pre-made servo board Tony is talking about, it's I2C so should work and should be straight forward to script for.
Yes , I have 3 EZB's running in my B9 but it's mostly because it's a level thing. Each level of B9 twits, bobs or bends so I wanted to keep the wires running through these areas to a minimum. With an EZB on each level (Legs, Torso and Bubble) all I need is a power cable.
Furthermore, The EZB in the torso where most of the electronics are, I'm down to two digital ports and no ADC ports. I still have to build my arms with servos and sensors that will be controlled and powered from the torso section. I'll need more ports for sure. My plan was to buy another EZB (if they ever get released). With your little gizmo I may not have to buy another one and also free up a lot of processing power.
With that said, Sure! Please through it into the box with the motors. You're a kind and generous man.