Arduino "Time and The Rani" working Tetrap wrist communicator prop build

[rustymetaldog]

Okay... where to start...!

I'm building a full-size Tetrap, and need a communicator bracelet to go with him. I'm serious!

Some of you may already have seen my sculpture in progress in the Facebook group "Doctor Who masks, props and studio scale models"?



...and this is where I am at with the communicator...



So, hopefully you can see I am serious

I've bought an Arduino Uno though think it's actually a chinese knock-off version, to try and make the 4 digit 7 segment display countdown from 9999 to 0004 as it did in the programme. I thought this would be the easy part! After a day of downloading codes, watching Youtube videos and trying to cobble it together, it has become the most frustrating part of the build. I guess electronics just isn't my thing, even though I built a full-size RC K-9, this has me stumped!

Can anybody unlock the gates to the wonderful world of Arduino? This could be a great open project, where we could all learn how to make all these Arduino bits and pieces do cool stuff - I'm thinking of adding soundclips and audio from the show to the communicator, a few flashing lights and a button or two, though I want it to actually DO SOMETHING. I can easily make it like a prop with a flashing LED behind acetate to make flashing numbers, but I want to move with the times and make a proper countdown!

If anybody can help me, it would be massively appreciated, I think this can be a great little project with a bit of help from you guys.

Thanks in advance...

Andy

[galacticprobe]

I've bought an Arduino Uno ... to try and make the 4 digit 7 segment display countdown from 9999 to 0004 as it did in the programme. I thought this would be the easy part! After a day of downloading codes, watching Youtube videos and trying to cobble it together, it has become the most frustrating part of the build.

I share your pain there, Andy. Software was never my strong point. I tried looking it up on Google (for giggles) to see if there was anything out there that might be more helpful, and there are thousands of hits for this. (You can try looking through this one http://forum.arduino.cc/index.php?topic=119010.0 to see if there is anything that you haven't seen yet. I have no idea what's really going on at the above link as things made my head spin when I read it - or tried to read it - but it did talk about a 4-digit countdown display using an Arduino.)

I guess electronics just isn't my thing, even though I built a full-size RC K-9, this has me stumped!

Don't confuse electronics hardware (the bits you built your RC K-9 with) with controlling software that tells computerized thingies what to do. They're completely different, so don't let this little hiccup make you second-guess yourself.

Can anybody unlock the gates to the wonderful world of Arduino?

I know there are several members on here with Arduino experience - some that make my head spin when I read what they've posted, so no doubt one of them should be able to help you out. (Our Arduino guys are really clever!)

Dino.

[rustymetaldog]

Thanks for the encouragement Dino!

I love the things that Arduino can do, but learning it.... well... I'll have to, I guess.

I love a bit of learning though, it's a real plus-side to making all of these mad things. Just thought it might be a bit easier.

I'm not giving up though

[pmc]

Your problem here is the number of pins required to drive four 7 segment displays is quite large and the Arduino alone cant do it. You need to buy another chip that along with the Arduino can do what you want. I am doing a similar project (Back To The Future time circuit clock) and am also driving it using an Arduino. I have bought one of these to drive the 7 segment displays http://www.ebay.co.uk/itm/351565170849?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

This can drive quite a number of 7 segment displays just using a few output pins from the Arduino. Another way to tackle it is to use a number of shift register chips.

Paul.

[rustymetaldog]

Any images Paul? I'm only using a single 4 digit display, not 4 x single digit displays if that makes sense? Keen to know how I can use less pins!

[jorwick]

Paul is right - the best way to drive this is with a separate IC that will tell your display what to do..  but can  you post any info on your 4 digit display?
I would expect it is one of two things :

1) a 4 digit display with built in ICs  already ready to be used with a CPU (something like this: http://www.ebay.co.uk/itm/TM1638-LED-Module-4-Digit-7-Segment-Digital-LED-Display-Module-for-Pi-Arduino-/322169998941?hash=item4b02d40e5d:g:QjYAAOSwjXRXb85N)
2) 4 electrically separate and individual 7 -segment displays that just happen to be connected as a single physical unit. This will have basically 8-9 pins for each 7-segment display. - something that looks like this: http://www.ebay.co.uk/itm/2-x-Red-0-56-4-Digit-Seven-7-Segment-Display-Common-Cathode-LED/282073165303?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D38540%26meid%3D2ddddfa627b44c5eacac7dedeaceb4e5%26pid%3D100005%26rk%3D2%26rkt%3D4%26sd%3D272060578665

Of the two - the latter is more likely.  Here is a decent tutorial  on how to do this with Ardunio and some specific decoding chips
http://playground.arduino.cc/Main/MAX72XXHardware


But basically  there is something called SPI.. which basically allows you to send data from the Arduino CPU to  an offboard peripheral  - using a software library that is already written for you.. ( My  Lights and Sounds controller uses SPI to tell my AMP  what volume to be)  

Typically this interface  is pretty darn simple..  the command is pretty much  "COntact device 7, and write the number 4 into its memory at location 2"

A device like these drivers  will know that 4 in binary is  00000100 -- and will turn on ( and keep lit)  the LED connected in the 3rd position (  where the 1 is)  while leaving others off.  Need two LEDs on?  Send different binary numbers - 5  would turn on  101 -  so the first and 3rd LED outpus respectively and so on..  7 Segment specific  driver chips will let you just send a number - like 5 and it will figure out for you what LEDs it needs to turn on..

https://www.sparkfun.com/products/9622 -  it looks like this chip can be put into either mode.

Obviously in the decode mode, you get the basic digits... . Doing individual segment control lets the CPU to make symbols that aren't digits. , or do chasers ( light goes around sequentially in a ring,  light goes up three segments bottom to top etc) or other effects...

SO the first thing you need to find out is if your display  has individual wires - allowing control of each of the segments,  or if already has that all built in and you are expected to interface with it in some other way.

Also, sound is sort of a PITA on Arduino.  You typically need to add another board , load sounds into it,  add a small amp, and a speaker and so on . Its one of the main reasons I went Raspberry Pi on my controller  its the built in sound.. For the Money, you can generally do more with a PI or other linux based machines.. Heck they are all ready to drive a HDMI based display, use a keyboard, upload and store sound files, etc.. . However, for props like this one, size constraints can become an issue, so the smaller Mini Arduino stuff  may  still be better in your application.

[rustymetaldog]

Jorwick - THANKS!!!

But... I'm using a 12 pin variety 4 digit 7 segment display with an Arduino Uno, not like the examples you posted! I've got my code almost sorted out, and am introducing some switches to make it start/stop etc. Learning all the way...

Agree that size will mean I will have to upgrade to an Arduino nano to fit it all inside, but I think this will work fine.

The sound seems to be straightforward enough with the shields available - will post videos when there's something to show...

Thanks again for your great reply - cheers!

Andy

[jorwick]

But... I'm using a 12 pin variety 4 digit 7 segment display with an Arduino Uno, not like the examples you posted! I've got my code almost sorted out, and am introducing some switches to make it start/stop etc. Learning all the way...

Okay, that sounds like  its just 4 individual displays with a built in ICs for each.  But as long as you got it sorted, it doesn't matter what you use.  Good luck .