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16  Forum 2005-2010 (read only) / Troubleshooting / Re: do stepper motors need buffers?? on: January 16, 2006, 11:29:19 pm
thanks Daniel! I wired everything as you suggested, e voila! she lives  smiley-grin
17  Forum 2005-2010 (read only) / Troubleshooting / do stepper motors need buffers?? on: January 15, 2006, 09:19:27 pm
I am investigating controlling stepper motors with the A-board.

I know that you can buy a stepper motor controller IC, but I want to do things the hard way smiley-wink

So, now I am trying to control the stepper motor using a TTL 74194 shift counter, a hex inverter (for direction control) and a darlington transistor array. (don't be impressed! - I am just following the instructions in a book!)

Amazingly this seems to work, however, the book recommends using a hex buffer before the darlington transistor array to (and i quote....)

'..protect the translator circuit from the motor's supply voltage in the event of a transistor-to-base breakdown.'

Anyway I tried connecting up a hex buffer (sn7407n) and now things don't work. smiley-sad

I'm sure that this is a mistake in my circuit (i'm a electronics beginner) but before I try again, i wanted to ask.... is the buffer needed?? I notice on the 'Unipolar Stepper Motor' tutorial, there is no buffer being used. What do you guys recommend??

Kind Regards

18  Forum 2005-2010 (read only) / Troubleshooting / Re: How to use a hex inverter??? on: January 04, 2006, 06:42:10 pm
whoops! how embarrassing!!!

yeah, i put that line in at one point, when I was trying to debug things and I forgot to remove it. without it, everything works as expected!

I put a scratch through that line, so that anybody looking at this thread can easily see what was wrong.

I hope the pictures will be useful to anyone else trying to do the same thing.

Thanks doctor - I'll try not to waste your time in future!!
19  Forum 2005-2010 (read only) / Troubleshooting / Re: How to use a hex inverter??? on: January 03, 2006, 11:00:27 pm
hi David,

thanks for the help.

here is a picture of my circuit....

the long orange wire is the output, 'A' in my circuit diagram.

the two green wires are connected back onto the arduino board, for the purposes of testing. they are B & C

the resistor is 10Kohms

This is the 'quick and dirty' program I have on the arduino board to test the circuit...


int inA = 0;
int inB = 0;

void setup()
 pinMode(11, OUTPUT);  
 pinMode(9, INPUT);  
 pinMode(8, INPUT);              

void loop()
 digitalWrite(11, HIGH);

 inA = digitalRead(smiley-cool;
 inB = digitalRead(9);
 if (inA == 0) printByte('0');
   else printByte('1');
 printByte(' ');
 if (inB == 0) printByte('0');
   else printByte('1');

 digitalWrite(11, LOW);

 inA = digitalRead(smiley-cool;
 inB = digitalRead(9);
 inA = 0;
 if (inA == 0) printByte('0');
   else printByte('1');
 printByte(' ');
 if (inB == 0) printByte('0');
   else printByte('1');



i get the following repeating output in ZTerm

h   0   1
l   0   0

meaning that when A is High, B is High and C is Low
and when A is Low, B is Low and C is Low.

So, something is obviously wrong.

what does the digital doctor suggest??
20  Forum 2005-2010 (read only) / Troubleshooting / How to use a hex inverter??? on: December 27, 2005, 05:35:38 pm
I'm trying to use a hex inverter to create a DPDT switch which can be controlled by a single pin on the arduino board.

Below is a bad drawing of my circuit (Please forgive me - I am an electronics newbie!)

A is connected to a pin on the arduino board.

The idea is that when ...

A is HIGH,     B is HIGH and C is LOW
and when ...
A is LOW,     B is LOW and C is HIGH

Anyway, its not working. I guess i'm doing this totally wrongly. Could somebody please put me right??

(merry christmas! to you all and I wish you a geeky 2006!)
21  Forum 2005-2010 (read only) / Interfacing / Re: Dimming an AC light on: June 12, 2006, 02:14:40 pm
Oh Massimo! I love you're brain! Give it to me!!!!

22  Forum 2005-2010 (read only) / Interfacing / Dimming an AC light on: June 11, 2006, 05:04:48 pm
I want to have dimming control of two AC lamps from arduino.

I've been investigating my options but I'm not sure what is best.

Option 1: Get a DMX dimmer unit and control with the DMX control unit code in the tutorials.

Option 2: Replace the potentiometer in a standard light socket dimmer with a light dependent resistor and control with an LED connected to arduino.

Option 3: Use a light dimmer kit which accepts a 0 - 10V DC analogue control signal. (but how do I create the control signal using the arduino board??)

Can anybody advice which option would be best / easiest?? Is there another option I should try instead??

Thank you!!
23  Forum 2005-2010 (read only) / Interfacing / Re: controlling a relay on: July 18, 2006, 05:06:35 pm

(I think/hope this is correct...)

One way to control a relay from the arduino board is to use a transistor inbetween. As follows...

the input goes to the arduino output pin. When the pin goes high (or low - depending on the type of transistor) the transistor allows current to flow and activate the relay. The plus is 12V. I believe you can use a standard darlington transistor array.

You could also use a optoisolator IC, instead of the transistor.

Regards // Jonathan
24  Forum 2005-2010 (read only) / Interfacing / Re: Simple AC motor On/Off on: July 19, 2006, 05:36:38 pm
Thanks Massimo! SSR is the answer!

And I'll go for the pre made version.


I want to turn on and off a single phase, capacitor start, AC motor. low frequency - on for 10 secs, off for 2 minutes.

1. Does it matter where I connect the SSR in the AC motor circuit? Can I just put it anywhere on the supply line? or do I need to take the capacitor into consideration??

2. As far as I understand it, all I need is the arduino board, the SSR, the motor and motor start capacitor. Is it really that easy?? No diodes, resistors or capacitors?? (please say yes)

3. Excluding voltage and current ratings, is there anything I need to consider when choosing a SSR??

4. Are all SSRs opto-isolated??

Sorry for all the questions..... Thanks for all the answers!.....

25  Forum 2005-2010 (read only) / Interfacing / Simple AC motor On/Off on: July 18, 2006, 05:14:51 pm
I want to turn an 240V AC motor on/off with the arduino board.

Which is the best way??....

1. Optoisolator + Relay
2. Darlington transistor + relay (do I need protection diodes??)
3. other... (please suggest)

Please save me from my ignorance!!

Thank you!

26  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: PCB manufacturers? on: March 19, 2006, 04:41:02 am
Thanks!!  smiley-wink
27  Forum 2005-2010 (read only) / Frequently-Asked Questions / PCB manufacturers? on: March 18, 2006, 11:00:05 am
Can anybody recommend a company in Europe which does cheap, low volume PCB manufacturing??


Flat Stanley
28  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: DC, Servo or step motor? on: January 15, 2006, 08:55:16 pm
Hi Michael,

can I ask which stepper motor driver you are using??


29  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: led driver on: December 06, 2005, 10:51:28 am
Thats great!

i'll report on my experience of using the chip!

Thank You!


30  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: led driver on: December 05, 2005, 03:24:20 pm
Hi David,

is there a more generic name for the 4794??

i'm trying to find an equivalent chip from RS (as I have an account with them) ( but when i search for led drivers, i don't find the right sort of chip

Is it a multiplexer?? or ...???

Thanks a lot


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