My contribution to the increasing entropy, and eventual heat death of the universe
Archive for the ‘Uncategorized’ Category.
I decided to have a poke around in one of the Picomotors I bought. The construction is fairly simple. I’ve annotated the above picture and it matches the description in the product documentation well:
A nice neat little construction! More pics below:
I’ve written about slip-stick motors before here and I’ve now purchased a couple from ebay to play with.
I acquired both 30nm and 100nm resolution Picomotors and a Picomotor 8701 driver. This post documents the process on getting them up and running.
This is the 30nm resolution motor:
It’s kind of seen better days. The case is coming off and I wrapped teflon tape round it to hold it together. It does work however!
Slip-stick motors work using the difference in motion caused by static and dynamic friction. It’s rather neat and you can read more about it here. But it means they only require a single piezo stack give clockwise and anti-clockwise rotation. Giving you 30-100nm resolution over ~25mm travel.
The 8701 driver didn’t come with a power supply, but luckily it’s quite well documented (local copy). It requires +12,-12 and 5V supplies. It also used an old DIN type connector. Unfortunately I didn’t have one knocking around so had to make do with board pins. Hopefully the one I’ve ordered from China will turn up in the new couple of weeks, same goes for the 15pin input signal connector.
For the moment I’m running it off a bunch of lab supplies, but will probably put together something more permanent at some point:
Driving the motor is pretty straight forward. There’s a 5v “step” input pin (which triggers on the negative edge), and a direction pin. The motor can be driven at upto 1KHz. Initially I drove it using a function generator:
Finally I knocked a quick Arduino Sketch together to drive to motor over serial (code below):
void setup()
{
// start serial port at 9600 bps and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for Leonardo only
}
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
}
int cspeed = 1;
void do_steps(int dir,int dspeed) {
digitalWrite(9,dir);
for(int n=0;n<dspeed;n++) {
digitalWrite(8,1);
delay(1);
digitalWrite(8,0);
delay(1);
}
}
void loop()
{
// if we get a valid byte, read analog ins:
if (Serial.available() > 0) {
// get incoming byte:
int in = Serial.read();
if(in == 'W') {do_steps(1,cspeed); Serial.print("S");}
if(in == 'S') {do_steps(0,cspeed); Serial.print("S");}
if(in == 'P') {cspeed++; Serial.print(cspeed); Serial.print("\n");}
if(in == 'L') {cspeed--; Serial.print(cspeed); Serial.print("\n");}
}
}
I picked up this cheap Chinese Z-stage on ebay, it was only 100USD and I wasn’t expecting much but it’s actually pretty well put together. It uses a standard micrometer head and I could fit both a Picomotor and the Chuo Seiki AMH-13 in its place (which works well).
The micrometer head provided (pictured below) is easily the nicest micrometer I’ve seen come out of China. Very smooth and clean, there does seem to be a small amount of grit left in there but overall very nice (particularly considering the price).
The linear guides also look very nice, and the overall operation of the stage is very smooth.
I picked up a X stage which uses a Chuo Seiki AMH-13 auto micro. The auto micro uses a coreless DC motor and of course came without a driver.
It turned out to be pretty simple to drive, requiring only a DC voltage somewhere in the region of 1 and 5V. When I was testing it I set the current limit to 200mA and it appeared to consume between 100 and 200mA.
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