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91  Using Arduino / Project Guidance / Re: large drum-bot on: March 05, 2012, 11:49:57 pm
Just to wet your appetite-
92  General Category / General Discussion / Re: guide for a newbie on: March 05, 2012, 02:42:37 pm
 I have never used it but it did look interesting.

93  Using Arduino / Sensors / Re: Multiplex QTR-8RC line sensor on: February 24, 2012, 01:16:09 pm
Doesn't latch?

Have you actually got it to work without the multiplexer?  Do you know how this sensor works?

Basically you set the pin of the arduino to an output then drive it high to charge the capacitor of the QTR then switch it back to an input ( you would also need to turn off the internal pullup on the pin) and see how long it takes to go low depending on how much light is reflected back to the sensor.

With the 4051 which is just a bi-directional switch you would first set the address of the sensor that you would want to look at then do what I described in the last paragraph. This only looks at one sensor at a time but the process can happen pretty fast.

The sensor type you have was meant for processors that do not have an analog input capability (like the basic stamp) which use the time of discharge to figure out the analog value.

There are other analog switches that can look at more than one at a time. I just gave the one that would take the least amount of pins (4) to read 8 sensors.

Maybe a slick way to do it would be to use a pin change interrupt to sense when the pin has gone low and just cycle thru them in the interrupt and that would let you do other things instead of sitting in a timing loop.
94  Using Arduino / Motors, Mechanics, and Power / Re: help with a relay problem on: February 22, 2012, 06:49:53 pm
If it worked great when you first got it hooked up but now that you have the other stuff hooked up and it doesn't work now have you tried to remove the rest of the stuff and just have only the relay board hooked up to see if it is indeed not working ? I don't know if you followed the example code from the product page but I think it would be wise to avoid using pins 0 and 1 since they are used for the serial link. That bit you mentioned about it seeming to work when pressing reset makes me think there might be some hope for it. Just hook up it up to say pin 2.
95  Using Arduino / Sensors / Re: Salvaged PIR Sensors from an Alarm System on: February 22, 2012, 03:22:04 pm
Just a guess but the "C" could be common and the "NC" could be normally closed. Take a continuity reading between them when the sensor is off and when the led is on.
96  Using Arduino / Sensors / Re: Multiplex QTR-8RC line sensor on: February 22, 2012, 03:16:34 pm
Maybe an analog multiplexer like the 4051. It needs 3 lines to do the addressing for 8 io and 1 for the enable (which can be be hard wired to be always on thus eliminating that one pin). You have one common io that goes to your arduino and the other 8 go to the sensor board.
97  Using Arduino / Motors, Mechanics, and Power / Re: RC servo instead of a geared motor? on: January 30, 2012, 02:04:02 pm
You didn't say if you were looking for a continuous rotation but more than 270degrees. If you still want some control of position and have about 360 degree of travel then look into a type of servo called "winch servo" . There is even one that does about 3.5 rotations (HS-785) .
98  Using Arduino / Installation & Troubleshooting / Re: Arduino Uno board only works with digital pins on: January 24, 2012, 09:30:42 pm
Some breadboards do not have the power strips continuous so be aware of that in your setup on it. The color stripe is a good indication of how the power is routed.
99  Using Arduino / Project Guidance / Re: Arduino stepper controller on: January 23, 2012, 03:26:28 pm
Just thought I would throw out some old stuff to chew on. As a toolmaker from the 70's before there were cnc's there were nc's which basically ran from paper tape and did the moves without the use of a computer (just plain old ttl logic). Our shop had a Lagun mill with a 2 axis stepper that could do lines (G01) and arcs (G02 & G03). The arcs were limited to a quadrant. So to do a whole circle took four steps if starting on a axis or five steps if not. Since most of the guys in the shop were old school and did not want to learn something new I was the one who used it.

Started my own shop and the guy I worked for turned the mill into a manual one and gave me the steppers and the control box. I did adapt it to a mill and got it working but the control was getting flaky. Did a little poking around inside and basically it was using rate multiplier chips to do the linear and circular moves. From that I programmed my commode 64 to mimick the same idea but in assembly.

At the time Bridgeport had older 3 axis machines (nc using ttl circuits) which moved the knee instead of the quill for the z axis and the newer cnc ones which did move the quill. Funny thing is that Bridgeport still used the ttl hardware for the newer cnc ones. The computer would just do fancy stuff like scaling and rotation and etc. but the driving of the steppers was still using the old ttl logic just being fed by the computer rather than by the paper tape.

Pretty much the idea used was that everything is moving at a "rate". A 2 axis move is only a right triangle with the x and y being the cosine and sine which are fixed whereas in a circular move the rate of change for the cosine is the sine and vice versa. With rate multipliers and some control logic this was how it was done in the controller that I was given.
100  Development / Other Hardware Development / Re: Weird L293D and SN754410 behaviour on: January 22, 2012, 07:33:56 pm
Chip in backwards?  Pin1 is nearest to the end with the notch.

For better response post in the motors... forum.
101  Using Arduino / Motors, Mechanics, and Power / Re: Double BTS7960B 43A Motor Driver question on: January 19, 2012, 09:41:54 pm
You gotta love that shipping charge!

What about the power to the board for the motor?
102  Using Arduino / Project Guidance / Re: Stepper driver interference/noise ? on: January 19, 2012, 04:38:19 pm
Have never used the stepper library and do not know how the pulse is done for the step (on time versus off time) but you will notice that the driver you mentioned likes to see a "low" rather than the usual "high" for the step because of the way they did the opto-isolation of the inputs. You can see the logic inverter ( transistor ) pictured in the "User MCU " . Have not looked into it but see if the library allows the inversion of the step signal.
103  Using Arduino / Motors, Mechanics, and Power / Re: Question on servo motors on: January 18, 2012, 06:53:18 pm
Could not tell from your post if you have the external power supply ground hooked to the ground of the arduino board and the servo ground (common ground ) but it needs to be for the proper opperation of the servo.
104  Topics / Robotics / Re: Devantech SD21 servo controller and desperate programmer, after one year... on: January 14, 2012, 06:07:02 pm
I just did a quick glance at first but now I see you are extracting the low and high bytes from Pos_ms. Why not just use the lowbyte and highbyte functions on your Pos_ms integer.
105  Topics / Robotics / Re: Devantech SD21 servo controller and desperate programmer, after one year... on: January 14, 2012, 03:57:26 pm
Change 255 to 256
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