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46  Using Arduino / General Electronics / Re: strange diode reading with 5v relay on: October 06, 2012, 04:55:41 pm
ok further testing and i noticed its as soon as i ground the relay that the diode give the funny reading. perhaps i am doing something different with my grounding in this circuit. how separate are you supposed to keep the ground from a 12v psu and the regulated current from a 7805? can the arduino and other components take the ground from the 12v psu? or do you make a separate ground from the 7805 center pin? ground is so confusing!
47  Using Arduino / General Electronics / strange diode reading with 5v relay on: October 06, 2012, 04:32:41 pm

I am using a 5v reed relay with a coil resistance of 250ohms, and contact ration of .5 amps and nominal current 20mA.

I have the same relay on a breadboard and in a perf board and it seems to be soldered together the same way. When it is in the breadboard, the relay and diode on its coil works. On my multimeter I get a normal reading...(when I put the multimeter on ohms, one side gives a reading, the other does not) however this same circuit in my perf board, when I test the diode, i get a reading on both ends...meaning when I flip the + and - on the multimeter i get a reading of like 200ohms either way...when I take the diode out of the perf...the reading is normal again...the diode works.

Any idea what could be causing this?
48  Using Arduino / General Electronics / Troubleshooting ideas? on: August 24, 2012, 06:12:56 pm

I know the likelihood of this problem being solved isn't too high...but I thought I'd try.

A few months ago I made this kinetic sculpture (video of it in action and code is on the page):

It's basically two motors, 2 sensors, 4 relays and some LEDs. When a sensor is tripped the relays reverse the polarity of a motor or stop it and some LEDs flash.
The sensors are in analog and when they go higher than 20 the atmega tells the relays to turn on the motors. This worked great. I had it running in a gallery for a month straight, 8 hours a day, 5 days a week. I crated it up, moved it, and now I want to rebuild it. I put it all back together just like before and it's like the chip does not even notice the sensors....the only time the sensors ever seem to trip is when I first plug the machine in and it runs only one of the conditionals I have that the sensors trip...whether or not the sensor is actually being tripped. But that's it. The sensors are working (they have little LEDs that are normally on and when they're tripped the LED goes off), the relay coils work, I tested them, I multimetered everything I could and it seems like current is flowing....I reflashed the program onto the atmega...same thing. The one motor keeps going counterclockwise and it's like the sensors aren't even there...when they're unplugged it basically does the same thing just without that first if conditional being activated.

I don't want to totally rebuild this circuit board but just in case, do you guys have any other troubleshooting ideas I could use to solve this?

Thanks so much for any help!
49  Using Arduino / Programming Questions / Re: arduino mega and processing problem on: August 24, 2012, 12:12:13 pm
problem solved by uploading SimpleDigitalFirmata to arduino rather than StandardFirmata
50  Using Arduino / Programming Questions / arduino mega and processing problem on: August 24, 2012, 11:56:01 am

I am having a strange problem and banging my head into the wall.

I have some code on arduino (a Mega) that works fine but when I transfer that code to processing/Firmata using the arduino library it doesn't seem to work. I just want to push a button and have things happen on the computer.

So with the arduino code I have:
if (digitalRead(53)==HIGH) {
    digitalWrite(13, HIGH);

And with processing I have:

import processing.serial.*;
import cc.arduino.*;

Arduino arduino;

void setup() {
  size(470, 280);
  arduino = new Arduino(this, Arduino.list()[1], 57600);
  arduino.pinMode(53, Arduino.INPUT);

void draw() {

  if (arduino.digitalRead(53) == Arduino.HIGH) {
    ellipse(280, 280, 280, 280);

But yet I cannot get that ellipse to draw. Oddly, if I change the HIGH to a LOW in the code and run the program, the ellipse is there. So it seems to notice the button maybe....there must be some small thing I'm missing here! I tried changing the caps on Arduino and arduino but that didn't work, I have simplified the code so it's exactly the same as the Arduino code! When I run the arduino library test programs in Processing everything works fine so I know I have everything hooked up correctly....

 What am I doing wrong???

**edit: the OUTPUT test program works in the arduino library for processing but the INPUT program does not. Does the library not work with an arduino Mega?

***edit2: downloaded the mega library from here:
but in the library folder...nothing was there!!! So I got this one: but it still isn't working!
51  Using Arduino / General Electronics / Re: 5v relay and motor on: May 15, 2012, 09:38:19 am
i replaced the two relays. still getting the same problem. all the relays work. all the diodes work...i can hear the little reed relays making their clicks and everything. but when i hook up four to the arduino and then attach the external power (in this case 6v 300mA, and also a different adjustable one trying all different voltages and 500mA), the powersupply gets no reading on the multimeter...i don't even have the motor hooked up yet.... when i detach the power supply from the circuit, i get a reading again. What is going on?! This is all I have attached.

The relays are wired as such:

pin 1 - 6v, 300mA in

pin 2 - negative diode in, also connected to arduino pin

pin 3 - positive end of diode, also connected to gnd

pin 4 - going to motor
52  Using Arduino / General Electronics / Re: 5v relay and motor on: May 15, 2012, 09:26:17 am
ok i do have diodes across all my coils and i just tested them and they work. i desoldered two relays and now the circuit works. so i'm going to replace those relays and see if it works again. any other ideas? thanks so much for all the replies!
53  Using Arduino / General Electronics / 5v relay and motor on: May 14, 2012, 05:39:30 pm

I am trying to reverse the polarity of a motor using 4 little 5v SPST reed relays (because they're quiet). I built up a circuit with 4 relays in four arduino pins....two that are positive, ground and two that are ground, positive. I built the circuit, using diodes across the relay coils and everything. I was powering the motor separately with an 8v, .5amp powersupply and was powering the arduino with USB. Everything was working fine. I took out the USB and powered the arduino using the 8v, .5amp powersupply into the Vin pin. I let it run for awhile and everything was going fine. I came back, and the powersupply was broken and the circuit didn't work any more. I tried powering the arduino and motor sperately and still nothing....really strange things are happening....when I have the PSU in, I get a normal reading, when I hook it up to the circuit board, I get no voltage coming out when it's in the power/ground rails of the circuit board.

does anyone know what could be going on here? it's strange behavior....the only thing i could think of is that the PSU wasn't regulated and was giving me more amperage than .5 and the relays were getting stuck. but i pulled them out and they are still you think this circuit might work if i had a regulated PSU that was a steady .5amps as .5amps is the max current the relays can take....

these are the relays i'm using:
54  Using Arduino / General Electronics / Re: stepper motors and torque on: May 08, 2012, 05:29:51 pm
thanks for all the input....the motor has 4 wires....i don't know much about the motor...anything I know is from here:{F34339A0-00FE-48A1-AEB0-3833FA04664B}&vid=153687&comp=38&RegEvent=new

Step Angle ---------------------------------------- 1.8 deg

Ambient Temperature --------------- -25 to +40 deg C

Temperature Rise ------------------------------------- 85K

Insulation Resistance ----------500VDC 100Mohm Min

Insulation Class ------------------------------------------ B
Performance Specifications
DC Voltage    4.4 VDC
Holding Torque    297 In-oz
Rotor Inertia    0.0283 oz-in-secĀ²
Motor Type
Stepper Construction    Hybrid
Step Angle    1.80 degrees
Shaft Orientation    In-line
Gearing Options
Gearing    Motor Only (No Gearhead)
Housing / Enclosure
Units    Metric
Motor Shape    Square Body
Operating Temperature    -13 to 104 F

If you think I can't drive this with the you know any way I could drive it? Do you think once I properly drive and power it the torque might all of a sudden get strong? I can move the shaft around with my that normal on a stepper?
55  Using Arduino / General Electronics / Re: stepper motors and torque on: May 08, 2012, 02:57:02 pm
thanks so much. i'm using the easyDriver:

From what I understand you just give the EasyDriver has a built in regulator and takes care of powering the motor. Do I understand this correctly? I've slowed the speed waaaay down to no avail. could it just be this EasyDriver in combination with the motors I've been using?
56  Using Arduino / General Electronics / stepper motors and torque on: May 08, 2012, 01:45:42 pm

I was trying to use a few different stepper motors for a project to swing a 6oz pendulum. i bought a normal little one on sparkFun and also this one:

These things seem to have NO torque whatsoever. I can stop them from rotating with my pinky. I can't get it to lift or move or turn anything besides its own shaft. Is this normal? What are stepper motors used for typically? I was using this code:

Is there anyway to increase torque with the code?

Thanks for any advice...
57  Using Arduino / General Electronics / Re: electromagnet and PSU on: May 04, 2012, 01:59:14 pm
i don't have diode on the electromagnet...just on the tip120...should i use a diode on the electromagnet also?
58  Using Arduino / General Electronics / Re: electromagnet and PSU on: May 04, 2012, 11:01:31 am
Yeah...that's what I figured. But basically...I have the relays hooked up all fine. they are working. they are 12V, controlled through TIP120 transistors with a 1k resistor to the arduino...I'm using diodes and everything. I've used these for other projects with no problems. When I put the two wires coming out of the electromagnet one way into the relay coil...everything works fine...when I put them the other way...the PSU stops giving me power and the little green light on the PSU box dims and starts flickering....

I'll try to type out the schematic:
     DPDT relay (I know I don't need this big of a relay but It's all I have lying around at the moment and I'm just using it as a SPST)
    1              2 (pin 1 to TIP120, to GND, pin 2 to 12V)

     3             4 (pin 3 in 12V, pin 4 to GND)
    5---coil----6 (electromagnet plugs in here....this is where when I reverse it everything gets weird)
    7             8 (nothing in these pins)
59  Using Arduino / General Electronics / electromagnet and PSU on: May 04, 2012, 10:37:53 am
I'm trying to use some elctromagnets with an arduino...building them exactly as shown here:

that project calls for a PSU at 3.3 amps, 12V...I have a 12v psu at 5 amps.

When I put the electromagnet in my circuit...just using it with some 12V, 5amp relays...if I have the polarity of the electromagnet one kills the PSU and I get no power...when I reverse the polarity of the wires...everything works fine in the circuit. I'm just curious why this would be...I haven't messed around much with making electromagnets before. They're very curious!

thanks for any info!
60  Using Arduino / General Electronics / Re: pendulum on a string on: May 03, 2012, 02:14:53 pm
thanks so much for your help. I'm having a real hard time finding a suitable stepper motor for this....i got one from sparkFun awhile ago that has practically no torque. it's a bipolar and i'm using the easyDriver with it.
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