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976  Using Arduino / General Electronics / Re: Increase emitter current NPN transistor on: February 06, 2012, 01:48:41 pm
Typically you would use a PNP transistor for a High Side switch. It would also require a resistir between the positive supply and the base and an NPN transistor between the Base and ground.

An NPN transistor is used as a low side switch with the base driven straight from the Arduino.

A High Side PNP transistor needs the Base voltage to be approx 0.7 volts below the positive supply for the transistor to turn on. If the Base is at the same voltage as the posotive supply the transistor turns off. To drive this from an Arduino you would need a resistor from the positive supply to the base of your PNP transistor, and an NPN transistor between the output transistor base and ground, and the base of this NPN to your arduino.

A Low Side NPN switch needs it base approx 0.7 Volts above the negative side of the supply to turn on and at 0 volts when off.

A High Side NPN switch would have to have its base at a voltage approx 0.7 volt above the voltage at the input terminal to your load. As the load is a motor this voltage would be variable depending on the load and thus would make for a difficult situation to control accurately.
977  Using Arduino / Programming Questions / Re: How to modify the stepper pins from a PC on: February 06, 2012, 12:48:24 pm
Since you are controlling this from your PC and serial port, why worry about tHose settings in the Arduino - just send it the number of steps you want and do the housekeeping in the PC.

You can drive more steppers from the Arduino if you make/get some driver boards that woulds only use 2 control wires - 1 for step and 1 for direction. Depending on how many motors are running at one time you could have multiple motors direction inputs tied together as long as you only drive one of them at a time, or keep track of those that can run the same direction and only run those together. As is, on an Arduino you could drive 6 step & direction type controllers. (And you could program a ATTiny2313 or similar chip as the brain in the controller driving the transistors/bridge connected to the motor.)
978  Using Arduino / Installation & Troubleshooting / Re: BURNING BOOTLOADER IN ARDUINO DIECIMILA on: February 06, 2012, 12:34:45 pm
Do you know anyone with an working Arduino board? You can program it to function as an ISP and use it to load a bootloader in your device.
979  Community / Bar Sport / Re: Things don't work so well on 70 volts ... on: February 05, 2012, 10:13:21 pm

Therefore, something goes wrong in the USA, we going down too here in Canada.   

zHey - We were taught to share here...
980  Using Arduino / Microcontrollers / Re: aTmega328s so fragile??? on: February 05, 2012, 09:37:11 pm
Unless you are programming a bunch of chips you aught to look into using your Arduino as an ISP. the wiring is simple and it is easy to use, I find it painless and built a small board that I connect up to ma Arduino and program my chips. I have been programming ATTiny2313 and ATMega328 chips with no problem.
981  Using Arduino / Installation & Troubleshooting / Re: Possibly defective board (random triggering of digital inputs) on: February 05, 2012, 09:07:32 pm
The problem is called a "floating" input. Unless you tie it to either +5 or ground through a resistor it is somewhere in the middle. Depends on what signals are in the environment of that pin. Think things like florescent light noise, radio frequency noise (cell phones, wireless devices...) al can put a strong enough random field at an unconnected pin for it to read constantly changing values.

The only time it won't work is when you want that condition to exist, it will then stay at either 0 or 5V...
982  Using Arduino / Motors, Mechanics, and Power / Re: Mechanics: Moving box lid up and down? on: February 02, 2012, 02:52:09 pm
2 shafts with 4 cams, shafts are linked together and operated by a servo.
cover is just floating on the cams.

2 shafts with arms and links, shafts are linked together and operated by a servo.
cover is retained by the links.
983  Using Arduino / Motors, Mechanics, and Power / Re: dc motor controlling by ECG signal value on: February 02, 2012, 02:48:56 pm
Amit -

If you want someone to write the code for you, you probably aught to go somewhere where you can hire a programmer.
If you want some advice then you probably should give some details about what your serial messages look like. This forum is a bunch of UNPAID folks trying to learn, and in some cases help others solve problems they encounter. That does not men that we wish to write your code for you. Show us what you got and what problem you are having and you would probably get a lot more help.
984  Using Arduino / Motors, Mechanics, and Power / Re: DC to DC voltage step down on: February 02, 2012, 02:08:22 pm
What you need is another "power supply" mainly a small stepdown transformer from 120 12 V AC. Go through a ful wave bridge rectifier and a regulator (7812) for your 12V needs, and through a 5 V regulator (7805)  for your 5 volt needs. All this is assuming you need less than 1Amp of low voltage DC. If you need more at 12V then you would have to size that part of the power supply for the 12V needs and still use the 7805 for the 5 V needs. A few appropriate Capacitors at each stage of the DC would clean it up and make the devices connected happy.
985  Using Arduino / Motors, Mechanics, and Power / Re: LIFA+servo position control on: February 02, 2012, 02:02:54 pm
A servo is a device that you control in Open Loop. In other words you tell it where you want to go and hope it gets there because it has no way of telling you it has completed the job. For closed loop you would need a feedback device - a potentiometer, an encoder, a bunch of switches...

Provided the servo is large enough for the intended application it works just fine. If it is too small, it may stall and never make it where you tell it to go.
986  Using Arduino / Motors, Mechanics, and Power / Re: MOTOR DIRECTION CONTROL on: February 02, 2012, 01:58:45 pm
Are your drives all set for step & direction? or are some of them configured with a forward and reverse pins?
987  Topics / Science and Measurement / Re: Differentiate between 1.0 VAC and 1.5 VAC on: February 02, 2012, 01:55:24 pm
TO read the AC voltage with an Arduino is going to require that you rectify it first - check your diodes carefully - they have approx 0.7 V drop. Bring your signal to the Arduino through a Diode with a Capacitor to ground to clean it up a bit and then to the Arduino. you will have approx 0.3 and 0.8 volts,

With a silicon Diode you have about 0.7 volts across the diode, Germanium about 0.3, but the silicon diodes are easier to find.
988  Topics / Science and Measurement / Re: New oscilloscope (without Java) on: February 02, 2012, 01:48:45 pm
Having a program on the Arduino that uses the serial port is no problem. I do it all the time when testing.
989  Using Arduino / Microcontrollers / Re: Little help with bootloading? on: February 02, 2012, 11:44:14 am
You don't need to buy a programmer - you Arduino can do that function - The ArduinoISP sketch on your Arduino board, mount yur new chip on a breadboard with your crystal/resonator, 6 wires from your arduino board to your breadboarded chip, a 120 ohm resistor from +5 to reset on your Arduino board. I made a little board that looks like this -
990  Using Arduino / General Electronics / Re: Using Arduino as ISP — Not able to programme anything on: February 02, 2012, 11:34:05 am
THis line right here has teh problem -

avrdude: Device signature = 0x1e950f
avrdude: Expected signature for AT90USB82 is 1E 93 82

AVR is expecting to get an ID response back of 1E 93 82 and your chip is responding 1E 95 0F.

If you are sure you have everything setup correctly and this is just a newer version of the chip you could add -F to your command telling AVRDudue to ignore the signature and program anyway. It looks like its there...

What version of Arduino IDE did you use to load the ArduinoISP sketch? if you did it with 1.0 there is a bug. Load the ArduinoISP sketch using 0.22 or 0.23. With Arduino-1.0 the ArduinoISP sketch only works at 9600 baud.
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