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Step 3Servo Thottle Control on the Drill
While you could use TRIACs and things to properly control the AC voltage going to the drill, we just used a servo to press the trigger. This drill is a variable speed, so controlling the trigger position allows control over the speed.
The key here is making sure the push rod (in our case, some scrap pcb) has enough freedom to rotate.
The screws proved to be a cheap, but effective guideway for the push rod.
The HS-311servo was plenty strong to push and hold the trigger, although it is helped by the linkage design a little. As the trigger is pushed further in, the mechanical advantage increases so the servo doesn't have to work as hard.
The speed is regulated mostly by a lookup table. We experimented to find out what servo settings led to what speeds, and then entered all the data into a table so the speed could be adjusted from 0 to 100. For any control buffs out there, a little integral control was added on top to home in on the desired speed.
The key here is making sure the push rod (in our case, some scrap pcb) has enough freedom to rotate.
The screws proved to be a cheap, but effective guideway for the push rod.
The HS-311servo was plenty strong to push and hold the trigger, although it is helped by the linkage design a little. As the trigger is pushed further in, the mechanical advantage increases so the servo doesn't have to work as hard.
The speed is regulated mostly by a lookup table. We experimented to find out what servo settings led to what speeds, and then entered all the data into a table so the speed could be adjusted from 0 to 100. For any control buffs out there, a little integral control was added on top to home in on the desired speed.
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