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Overview
This is a simple 4/5 servo robot arm. It is controlled by a vb.net app which sends out data over rs232 to a PIC.
The PIC then positions the servo to a position between 0 and 240. This version features gradual servo movement, and can support upto 12 servos in parallel.
This bot uses my BotBoard |
Software
VB.net 2008 application. This is an updated version of SSB's software controller. The main difference is the servos position as the trackbar moves. This allows 'real time' positioning and gives better feedback when programming moves. Again the app sends out servo data position depending on the position of the trackbar slider. To move the servo controlling the main up/down shoulder, slide the trackbar to a position and the servo responds directly. Data is send out over rs232 in ASCII bytes SERVONUM and X (the trackbar position) to the PIC.
The action script has been ehnanced adding 'real time' recording. This is usefull as you can record the speed of the servos moving to make fast then slow movements for example. It also allows for pauses in operation. When you play the script it simply loops through each entry and sends those values to the PIC. Action scripts can be saved and loaded. On script playback the bot automatically reverts to it's default position before playback.
Center buttons position each servo to it's center position 127. Reset robot centers each one in sucsession and clears the action script. A new featre "Set Default position" has been added. When clicked, this sends the current servo positions to the PIC EEPROM. When the botboard is powered up again, the servos will automatically move the the positions stored in the EEPORM.
In this version, all parameters are easily controlled in the code. You can set each channels PIC output, max, min and default (center) values by setting variables, making it very easy to fine tune the software to the hardware.
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Construction
This arm uses a total of 4 or 5 servos:
- 1 large (Futaba S3003): Main rotation
- 1 large (Futaba S3003): Main sholder Up/Down
- 1 mini (eSky): Elbow
- 1 mini (eSky): Wrist Up/Down (can be omitted, thus making 5 servos)
- 1 mini (eSky): Wrist Rotation
- 1 mini (eSky): Grabber
The base is a simple project box, and the arms are cut from L shaped alloy (the kind of stuff used to protect door corners etc). I chose the alloy because it is light, and give a good mounting surface for the mini servos.
The servos are held in place using double sided tape and further secured with tie-wraps.
All servo horns are fixed using 90 second epoxy.
The grabber is a simple design, using a servo to drive a gear, this then drives another gear in the opposite direction. The grab arms are made from 3mm "Sign board" laminated to make 6mm. The grabber cushions are draught excluder material. The arms are glued to the gears, which in-turn are glued to the servo horn.
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Images
Here are the images relating to the project.
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