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1  Community / Bar Sport / Re: searching for a robotic (arm) project? have a look at this! on: July 18, 2014, 04:03:26 pm
Quick enough for fencing Bob ?   :-)
2  Using Arduino / LEDs and Multiplexing / Double the output, ( or viewing angle ) , same current , half work for a MAX7219 on: June 20, 2014, 10:50:12 am
I have tried a search on this subject, but quite honestly the forum is so big now, that it takes ages to sift through the threads bought up.  This might be old hash .

Let me just run this past you guys....

I made a soccer scoreboard with 7x5 displays last year , Using the SAA1064 chip , which gave a 50% duty cycle , for max output from each LED.
I am now making some more boards using the MAX7219 driver.

I have arranged it this time with 5 columns across and 7 high .

This means I can set up in the register to limit to 5 columns, and skip the other 3, giving more brightness ,  20 % duty cycle, but still down on the 50% duty cycle of last years

The LEDs I am using this year are more than twice the output of last years ones, so I should be back on track with the actual  apparent brightness of last years project.

Now I have a request for a similar sign twice the digit size  ( 4 times the area ) but I have realised that I can put 2 red LEDS in series in place of the previous one ( each has 1v9 voltage drop ) and the chip should be able to supply Imax to both LEDs in series at 3v9

So in theory I can get twice the light output per column, using twice the number of LEDs, with the chip now running cooler, as it doesn't have to get rid of the extra ( 5 - 1.9 v )

But since  now I am saving the power dissipation in the chip, perhaps I can pulse the LEDs with twice the current as before ?  Giving me twice the light output for the same digit ?  ( OK at double the supply current, but there is no such thing as a free meal ! )

How does this sound ?

If you are not upsizing, you could tilt every other LED by half the viewing angle and get the same intensity as with one LED.

3  Using Arduino / Project Guidance / Re: bytes and nibbles on: June 16, 2014, 11:27:38 am
Too true.
4  Using Arduino / Project Guidance / Re: bytes and nibbles on: June 16, 2014, 10:13:48 am
Ans some tired old guys in the middle of the night still get them transposed  ,,,,   :-)
5  Using Arduino / Project Guidance / Re: bytes and nibbles on: June 16, 2014, 09:51:33 am
This thread shows absolutely the advantage of the Arduino community, I made a stupid mistake that my Great Grandson would not have typed , and instead of wasting a whole day finding it, you guys picked it up.

I am not interested in trying raspberries or whatever, I have had so much support ( even though I am still stuck in V22 until I can find a few hours to upgrade  my libraries to V1.05 )  and its working for me, who didn't have a clue about micros 3 years ago ( at 63 )
6  Using Arduino / Project Guidance / Re: bytes and nibbles on: June 16, 2014, 08:45:01 am
Not quite , more like  "  Ah, So "  :-)

7  Using Arduino / Project Guidance / Re: bytes and nibbles on: June 16, 2014, 07:50:15 am
Yes thanks, I had just spotted it and called myself a name that my wife often hears :-)

Thanks Guys
8  Using Arduino / Project Guidance / bytes and nibbles on: June 16, 2014, 07:22:57 am
I am busy just trying to put together some building blocks for my next sketch, and I keep tripping over this confusion on my part.  The top code works fine to display a 7x5 matrix character :-
   byte displayArrayA[5] = {63,63,136,72,72};
So I thought I would tidy it up by having a variable for the 0 -4 in each line :-

for (x=o; x<=4; x++ ) { 

But it tells me I am trying to convert an integer  to a byte or a byte to a byte, or whatever, I have tried all the religions when declaring the x , but am getting confused again.
I have searched and somebody had a similar hassle but it was to do with pointers that I havnt come across yet.

Feel free to tell me I am missing the obvious again.
9  Using Arduino / Project Guidance / Re: 7 changes to 0 on only 1 BCD switch SOLVED on: June 08, 2014, 03:17:02 am
sometime during debugging another hassle, I commented out line 2 here

 Serial.println("TX setup");              // for debug only
  // vw_set_rx_pin(0);
  vw_set_tx_pin(9);    //  Tx module connections and speed
  vw_set_ptt_pin(13); // powers Tx and LED

I must have added that at some previous time when I had a problem, but uncommenting solved it.

default pin for rx even if you are only using a transmittter is 11,  and I am using that to scan F,   so I guess the VW makes it an input.

Thanks for your time guys.
10  Using Arduino / Project Guidance / Re: losing eeprom value on: June 07, 2014, 08:51:36 pm
It wouldnt be an issue  in my application anyway, the data will probably only be changed once a month anyway, but I need to read the data after a power failure ( quite a lot here in Africa :-)

11  Using Arduino / Project Guidance / Re: losing eeprom value SOLVED on: June 07, 2014, 06:25:46 pm
Thanks for the replies guys,  you got it there Roger, when I removed the int from in setup, all is well.

I just want to get caught up with my 22 projects, and then read a bit more about all this stuff, ( and even update to V1  :-)  ) but at the moment its just juggling balls in the air, but it is great to have you guys for advice.

And I did just think about reading the eeprom for the display, but can't remember why I didnt, -  oh yes,  I was going to check if reading an eeprom had a life limit, but I dont think so ...
12  Using Arduino / Project Guidance / losing eeprom value on: June 07, 2014, 05:27:29 pm
One of the many little hassles today, is with a sketch where I store any incoming data in eeprom, with the idea of displaying this value after a power outage,

I have whittled it down to this
#include <EEPROM.h>   
int digA ;   

void setup()
  Serial.begin(9600); // Debugging only
  int digA = (0);  Serial.print("eeprom 0  =   ");  Serial.println(digA);
  Serial.print("digA read from eeprom =   ");  Serial.println(digA);
 void loop () {
  showtime ();
  delay ( 10000);
 void showtime ()
  Serial.print (" in showtime digA = ");
  Serial.println (int ( digA));
   and I already have the value 4 in eeprom (0)

when I run it I get on the serial monitor :-

eeprom 0  =   4
digA read from eeprom =   4
 in showtime dig A = 0

What happens to the value when I go into the showtime routine ?

13  Using Arduino / Project Guidance / Re: 7 changes to 0 on only 1 BCD switch on: June 07, 2014, 06:29:36 am
When I switched the E and F  scans, a completely different switch now wont send the 7.

I though it was the switch obviously, as the other numbers were fine, so that with its diodes was the first thing I changed.

I will have another look later, I have 4 things to get finished this weekend !
14  Using Arduino / Project Guidance / Re: 7 changes to 0 on only 1 BCD switch on: June 07, 2014, 03:51:45 am
Heres a circuit of a simple 6 digit version, if there are more digits I use daisychained CD4017s to sequence them all, with just 6 pins of the micro.
As you can see each switch has 4 diodes on it.

15  Using Arduino / Project Guidance / Re: 7 changes to 0 on only 1 BCD switch on: June 07, 2014, 03:18:23 am
Right,, the wiring is OK, this one only has seven BCD switches, you should see the one I did recently with 19 BCD switches.

I have made loads of these, and never had trouble with keypad or the scanning.

I will whittle the code down a bit later and see what is happenning.
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