Show Posts
Pages: [1] 2
1  Forum 2005-2010 (read only) / Interfacing / Re: IR hex code decoding on: May 29, 2010, 04:16:46 pm

You should start a new thread, your problem is not related to this thread.

And by the way, humans don't hear very well above 20 KHz so our audio equipment tends to stay below that.   Most IR controls are around 40 KHz.  So your audio recording is not likely to play back well enough for the receiver to recognize it as a valid signal.

There is an Arduino project for a universal remote, and another for web access.  Merge the two and your in business!
2  Forum 2005-2010 (read only) / Interfacing / Re: IR hex code decoding on: May 28, 2010, 02:42:49 pm

I think your interpretation is correct. However, consider these points:

1. The first number is "0000", which means "learned code" so the timing numbers might wander a bit.
2. On the 3rd page (irdisp3) they decode a Sony code and note that Sony "likes" to monkey with what data gets sent.
3. They also mention that there is no standard, and other mfrs can do as they please.

So, there is no guarantee that the code your looking at is a "simple" sequence of binary pairs.  Epson might have added in some other special numbers for their own nefarious purposes.  A google search might uncover their true meaning.

However, as long as the code sequence works - why worry about it?

I want to know how your going to use this data?

I guess the thing to do is set up a PWM at your modulation frequency, then turn it ON/OFF for the times given in the codes - just ignore the first 4 numbers, unless you want to make your software "smart" so it calculates the modulation frequency from the second number.

When I search Arduino for "Pronto hex" I get a bunch of hits, perhaps there is already some code for handling this?

I did a google search for "Pronto hex converter" and found lots of sites offering software to convert it into binary or hex numbers - but don't forget that might not work if those "odd" pairs are Epson-specific codes.

3  Forum 2005-2010 (read only) / Troubleshooting / Re: Question about MAX7219/7221 on: November 04, 2010, 09:07:18 pm
It is my pleasure to help those the same way I was once helped by others.  Heck, the way I am STILL helped by others!

We live on a very small, round planet that spins in circles.  Consequently we are dizzy all the time.  We need to work harder on working together instead of working so hard to pull apart from each other.

I use Eagle for my board stuff.  I recommend you get the free version, I certainly can post or send your schematics - time permitting.  

Eagle is very easy to use, even a programmer can figure it out.....   smiley-wink
4  Forum 2005-2010 (read only) / Troubleshooting / Re: Question about MAX7219/7221 on: November 04, 2010, 01:52:58 pm
I would try the 74HC04 since you have plenty.  

Assuming you are working on an experimenter's board where you just push wires into holes to make connections, its easy and fun to figure stuff like this out.

I can't recall off-hand if the 74HC04 series chips use voltage levels compatible with the MAX7219.  I would try that first. That is, put DIG0 and DIG1 into the 74HC04 and a voltmeter or LED/resistor on the output and see if it goes on/off when you put large numbers into the 7219.

In fact, since I prefer to build upon what works, I would put a standard 2 or more digit LED display on the board and drive that with the 7219 ALONE first - since it is designed to drive a simple LED display.

AFTER you get that working, then you can move the wire from the DIG0/DIG1 pins to your 74HC04 to see if it drives it.  Then makes sure it inverts the signal.  then add the MOSFET or whatever output drive of you choice - with the standard LED.

If that works, then replace the standard LED display with your real one.
5  Forum 2005-2010 (read only) / Troubleshooting / Re: Question about MAX7219/7221 on: November 04, 2010, 11:33:19 am
Oops!  I'm sorry "Silly(c)One", I did not actually answer your question.  And its a good one.

The MAX394 is an INVERTER.  Because the MOSFETS are non-inverting devices.  You give them a voltage to turn ON and take it away for OFF.

But the MAX7219 digit driver pin is INVERTED.  It goes to GROUND when ON and goes to +VCC when OFF.  They are using the 394 to invert that signal I think.

This is important, because it means if you want to replace the MAX394 you have to replace it with something that will invert the signal's logic.  Like an inverted digital gate, or a transistor, or something else.
6  Forum 2005-2010 (read only) / Troubleshooting / Re: Question about MAX7219/7221 on: November 04, 2010, 11:17:17 am
The IRF540 is a MOSFET and would work nicely.

However a lot of different manufacturers produce parts with that number, but not the exact specifications.  

The specifications from Vishay say theirs has an ON resistance of 0.077 Ohms (or 77 mOhms).  That is not very impressive.  There are devices available for the same or less price that have ON resistances (Rdson) around 0.005 Ohms (or 5 mOhm).  The lower the ON resistance the less power losses in the MOSFET (which are just a special type of transistor, by the way).

Which means, for example, if your running a light bulb (which takes a fair amount of current if its a bright one) a device with 77 mOhms ON resistance might need a heatsink or cooling fan.  Whereas one with 5 mOhms won't even get warm!

I'm old enough to remember when these things (MOSFETs) first became widely available. They were a novelty at first, since a "good" power transistor could do the same job better.  Now, these devices blow my socks off!  We can do power-projects that not that long ago were either impossible or needed BIG cooling fans..

7  Forum 2005-2010 (read only) / Troubleshooting / Re: Question about MAX7219/7221 on: July 22, 2010, 10:58:53 am
The MAX394 would work.  Its just a switch (two switches in one chip).  You could use a low-ohm MOSFET too.

All its doing is allowing the low-voltage output of the 7221 for multiplexing the displays to be "amplified" to whatever voltage/current your display needs.

As you noted, those big digit displays have multiple diodes in series.  That keeps the power draw down, but increases the voltage needed to switch them on.
8  Forum 2005-2010 (read only) / Interfacing / Re: 7 Segment Display using SPI on: July 20, 2010, 09:43:45 am
SparkFun now offers an alternative design.  This one has the interface pins along the top, so you can horizontally stack displays.

9  Forum 2005-2010 (read only) / Interfacing / Re: LED/ Seven Segment Display on: July 22, 2010, 11:06:29 am
Not exactly, the SparkFun kits are PER DIGIT. And would be very expensive, and very wasteful in that they are dedicating one CPU per digit - way overkill.

The 7221 and two 394s would allow you to run 4 digits.

And those are kits.  Either way, you will be soldering, but with the kits you would be doing a lot more soldering.
10  Forum 2005-2010 (read only) / Interfacing / Re: LED/ Seven Segment Display on: July 22, 2010, 10:46:32 am
Go back to the first posts I gave you!

MAX 7221

One chip that takes in serial input, and can drive multiple LED 7-segment digits.  In the datasheet for the MAX 7221 on page 12, Figure 2, they show how to use the 7221 with a MAX394 to handle large digit displays.

Some other interesting alternative chips:



The first one is a standard DIP package, and has the added bonus of supporting digital input switches and discrete indicators in addition to the LED display!  It is used in Vending machines.

The second one is an updated version of the 7221 but it only comes in a surface mount package.

I am refurbishing a machine built in 1977 that has a 7-segment display.  The old display was the best 1970's technology could offer.  I'm bringing it up to modern standards.  Which will mean it will be a LOT brighter, and support display of diagnostic codes to help fix the machine when things go wrong.

Like you, I don't like the thought of dedicating 4 output lines per digit - I can see a few choices.  I just ordered these parts so I can do a quick prototype of each idea and then choose.

From Sparkfun:
Arduino software for it:

From Digikey:
  - MAX7221ENG+-ND
  - MAX6959AAPE+-ND
  - 160-1576-5-ND (7-segment LED display, single digit, 0.56" tall)

My needs are simpler than yours.  That is, I just have to create a 1/2" tall display.  The Sparkfun module might be all I need.  Which would be great since its cheap and i'm lazy.

For me, the worst case would be if I will have to use one of the MAX chips and 4 LED digits on a proto board.  The chips are cheap, but it would take me a few hours labour to make the board. I've got my fingers crossed the SparkFun serial LED display fits inside the machine....

You have a more complex issue.  In addition to needing something to decode your CPU's data into the 7-segment LEDs.  Your output drive has to handle the voltage and current of a large display.

Sparkfun has a nice looking 6.5" single digit display:

Sparkfun has two kits they say are "good" for driving this large display:

These kits are awful expensive, but they would work.  The kits use a clever display driver from TI:

A TLC5916.  This chip is clever in that it switches the ground side of the LEDs, which allows the positive side to be anything up to 17VDC!  And the ground-side switch can control the amount of current flowing through it, regardless of the voltage. Pretty cool.

The data sheet is here:

This chip only handles ONE digit, so you would need one per segment.

Unless something else comes up, I think the 7221 is your best choice.

11  Forum 2005-2010 (read only) / Interfacing / Re: LED/ Seven Segment Display on: July 16, 2010, 11:36:49 am
oh yes, "experimentation" is the way to go!

12  Forum 2005-2010 (read only) / Interfacing / Re: LED/ Seven Segment Display on: July 16, 2010, 11:24:16 am
heh.   I should have looked first.  If you want "large" your only 7-segment choices are:

3" tall:

5" tall:

These are both ONE digit.  So you would want to connect 4 or 5 of these, as shown in the Arduino link I posted before and in the MAX 7221 datasheet.

Hmmm..   Looking at the datasheets for these two displays I think I see a problem.  They have wired multiple LEDs in series, which likely means the MAX 7221 chip won't put out enough voltage to drive them.

The data sheet for the 7221 shows how to use an external drive to boost power - more hardware work for you though.

Maybe the 8x8 array is the way to go after all?
13  Forum 2005-2010 (read only) / Interfacing / Re: LED/ Seven Segment Display on: July 16, 2010, 11:13:50 am
Don't panic when you look at these links, there is a LOT of choice out there.  We need to work through what YOU need to pick out the best choices for you.

These are common cathode displays:

These are common cathode matrix displays:

I have not gone through them, but I suspect these are only parts, no finished product.  Much cheaper, but you would have to do some soldering and assembly.  If you want something pre-fabricated do a google search.  Of course, there is no guarantee anybody has made a display as large as you want!  I think there is a good chance your going to have to make it yourself.

But don't decide today.  Give others a chance to read this thread and comment.

I have more design issues for you.  How far away will the display be from the information source?

This will affect your choice of driver chip.  The MAX chips has to be near the display, but the I2C interface can run a long way.  But if you use a cheaper chip, like the 74HC4511 (or any BCD driver) it might work better to keep the chip near the Arduino, and run long wires to the display.
14  Forum 2005-2010 (read only) / Interfacing / Re: LED/ Seven Segment Display on: July 16, 2010, 10:51:37 am
I need to know where you are, or at least what countries your comfortable doing business with to answer that question!

I'm in Canada (set your profile "location" for next time) and have had little trouble with vendors in Australia, Taiwan, Hong Kong, USA, UK and other EU countries.

The MAX chip can drive up to 8 digits or an 8x8 array of LEDs.  So your 4-5 digits won't be a problem.  If you want to do a scrolling display or any other fancy visual effect, you will want to build the 8x8 array of LEDS.  Because that will give you the hardware setup to do scrolling and other effects from within software on the Arduino.  Mind you, even if you "wimp out" and use 7-segment displays you can still do some fancy things.

The Arduino uses a special type of serial to talk to the MAX chip.  There is sample code with the Arduino IDE software.  Pretty easy to use.

You still need to tell the Arduino WHAT to display.  There are many ways to accomplish that.  What works best depends on some of the questions I asked you earlier: how often will the display change?

And where does the information to be displayed come from?
15  Forum 2005-2010 (read only) / Interfacing / Re: LED/ Seven Segment Display on: July 16, 2010, 09:25:30 am
It all depends on what information you want to display?  Letters? Numbers?

How many digits or letters?  How often will it change?  

Are you trying to scroll a message?

The link you provided goes to a funky meter that costs a LOT of money because it has a number of scientific inputs for working with sensors.  

If you don't need that, then you have much cheaper options.

You can purchase very large LED displays very cheap.  OR you can purchase (or make) an array of discrete LEDS.  Which depends on how you answer the first questions.

The good news is that regardless of which LED display you choose, the controls are the same and cheap:

This one is the "classic" example:

This one is newer, discussing a new chip - but it can be hard to get in some countries:

Keep in mind that there is also a "display shield".  While not as large a display, you could easily put multiple copies of it around the room and then use Ir to send around the information to be displayed.
Pages: [1] 2