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Topic: I"m lost and cornfused (Read 5473 times) previous topic - next topic

Naneen

I am retired and decided to play around with an electronic kit. I bought the Ultimate kit with Arduino Uno. Lots of parts and no instuctions.
I search on the web and found a book "Getting Started with Arduino" I now know how to program and make the single LEDS flash anyway I want to. I built traffic light with pedistren cossing. (I program industrial controlers for a living) the rest of the book is devoted to someother board and a sprinkler system. I live in a retirement home.  I get that the book and Arduino is to help make you think. I have never wired or program LED display or stepper motors nor do i know what some of the parts are that came with the kit. Enoght of this crying.

My current problem is trying to  work with the 4 digit 7 segment LED that came with the kit. I have found several example to wire and program the display with the board that I have. Problem is they have more pins then i do and i do not know the pin layout. The LED is SH5463AS this is a 12 Pin chip not 16 that I keep finding on the web. Some use diferent size resisters and other use transisters. I need to learn some basic facts.

I do have an electrical backround. I learned tube theory. very little digit theory. School during the 50's.

mrsummitville


DuaneDegn

Does this look like your 7-segment display?

https://cdn.sparkfun.com//assets/parts/8/7/3/5/12098-01.jpg

There's a datasheet available from the above link.

If this is the same display you're using, you'll want to use a 220 ohm resistors on the cathodes.

You'll want some way to drive the anodes since you wouldn't want to directly drive the anodes with a I/O pin (it could damage the Arduino to do so).

Edit: I see mrsummitville posted while I was typing.

Maybe, this will help ?

SH5463AS Demo
.
Where are the resistors?

Am I missing something? It looks like they're driving the display without resistors! Why?

DuaneDegn

#3
Dec 02, 2015, 09:31 pm Last Edit: Dec 02, 2015, 09:31 pm by DuaneDegn
I found the following in the program's comments.

Quote
This is an example of how to drive a 7 segment LED display from an ATmega
 without the use of current limiting resistors. This technique is very common
 but requires some knowledge of electronics - you do run the risk of dumping
 too much current through the segments and burning out parts of the display.
 If you use the stock code you should be ok, but be careful editing the
 brightness values.
IMO the above is hogwash. USE CURRENT LIMITING RESISTORS.

I think Grumpy_Mike as a good article on this topic. I'll try to find it and post a link.

DuaneDegn

Here's the quote from Mike's LED page.

Quote
There are several web sites and schematics on the web that suggest you can attach an LED directly to an Arduino output pin with no current limiting resistor. They are wrong, and following them will damage your Arduino. Their logic goes something like "the arduino will limit the current" or "as you are multiplexing the LED (turning it on and off rapidly) the circuit won't heat up enough to burn anything out".
They are wrong.

Naneen

Thank you for the post.

Mrsummitville Sorry but that one has too many pins.

Duanedegn

Wrong LED also.

The numbers on the package are SF R05 B03.

by the way, Thanks for the read on LEDs.

Just want to let all know I saw the Post. Going back to finish the article.

Will check back later.

Pat
My true name.


Naneen

Moved from Project Guidance.

I am retired and decided to play around with an electronic kit. I bought the Ultimate kit with Arduino Uno. Lots of parts and no instuctions.
I search on the web and found a book "Getting Started with Arduino" I now know how to program and make the single LEDS flash anyway I want to. I built traffic light with pedistren cossing. (I program industrial controlers for a living) the rest of the book is devoted to someother board and a sprinkler system. I live in a retirement home.  I get that the book and Arduino is to help make you think. I have never wired or program LED display or stepper motors nor do i know what some of the parts are that came with the kit. Enoght of this crying.

My current problem is trying to  work with the 4 digit 7 segment LED that came with the kit. I have found several example to wire and program the display with the board that I have. Problem is they have more pins then i do and i do not know the pin layout. The LED is SH5463AS this is a 12 Pin chip not 16 that I keep finding on the web. Some use diferent size resisters and other use transisters. I need to learn some basic facts.

I do have an electrical backround. I learned tube theory. very little digit theory. School during the 50's.

CrossRoads

A 4 segment display is usually wired something like this
http://cdn.sparkfun.com/datasheets/Components/LED/1LEDBLUCC.pdf
with either a common cathode for each digit, or a common anode for each digit. Use a 1K resistor from 5V and a wire to gnd to figure where your anodes and cathodes are to see which kind you have, and where the segment pins are and where the common pins are.
If cathode, you will drive the anode from 7 pins, each with current limit resistor, and sink one cathode low, for 2-3mS, , ,turn the cathode off, then do the same for the next digit, and repeat for 4 digits.
Do not let any one IO pin sink or source more than 20mA. I.e. if you sink the cathode with a pin, then limit each anode current to 20/7 mA.
If you use a NPN transistor to sink the current, you can drive more anode current and have a brighter display.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Naneen

CrossRoads Thank you for the response. But I have no idea as to what you are saying. Maybe I should stayed retire. I know that I can lick this and once I do i'll fly with it. but getting started is proving difficult.

I hook a wire to the 5V pin then to my breadboard through a 1K resistor, where does the other side of the resistor go?

If I am out of my league please say so. 

Naneen

#9
Dec 03, 2015, 08:18 am Last Edit: Dec 03, 2015, 08:23 am by Naneen
OK I ran a wire from 5V to a 1K resister. I also ran a wire from pin 12 to ground. when I touch a wire to pin 1 the first digit bottom left light comes on. What does that tell me? According to the print out that is E. Correct?

larryd

Welcome Naneen.
There are a few retirees here.
Another book of interest is Arduino Cookbook:
http://www.amazon.com/Arduino-Cookbook-Edition-Michael-Margolis/dp/1449313876

Starting with Crossroads PDF file, take a ~270 ohm resistor and 5 volts to test each segment in each digit.
This will give you some confidence and insight into the display.

+5v ----- 270 ------- a segment pin ------- cathode pin to ground
No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

larryd

No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

Naneen

LarryD

That is what I needed. Now maybe I can get started on to fun things. Thanks

larryd

#13
Dec 03, 2015, 08:39 am Last Edit: Dec 03, 2015, 08:47 am by LarryD
Slow but sure ;)
No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

PaulRB

Does your kit include a ULN2003 or ULN2803 chip?

If so, you could replace the 4 transistors and the 4K7 resistors with it.

Paul

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