Time machine display for my wife's school - ideas needed - Page 1
Forum section: electronics / projects

author: Stonent
author_rank: Super Contributor
timestamp: June 03, 2014, 11:30:38 pm
content: Background, my wife is a 3rd grade school teacher (ages 8 to 9) and teaches social studies. The curriculum for 3rd grade is "communities".She seemed rather excited the other day because she came up with an idea to update the area outside her classroom. (This is an area where things can be pinned to the wall). She said she wanted to know if I could come up with some kind of time machine theme for the area outside her classroom and build something electronic to go there. I asked her if this is something the school would be paying for and she said no, it's just something she'd like to do, so we need to keep the budget pretty low.My first thought was BTTF Time Circuits, but she said that would probably be lost on these kids who probably have not seen the movie. So her idea was something more space ship like. I asked her to google some pictures of something she'd like and she found some pictures of control panels with illuminated rocker switches, but also said she'd like it if it was somehow programmable where she could change a date easily so it could display the date of whatever historical thing she was going to be teaching about.Some thoughts I had:I've got hitachi character LCD that I could use, and also have 2 Noritake VFDs. I'm a little reluctant on the VFDs because I don't want them to break and shatter if they fall. I've also got a 4.5" 12V monitor screen that came from a in car DVD player. It has a single composite video input.Illuminated rocker switches look to be about the .60 to .75 USD price range through Tayda, those can add up fairly quick in price, but LEDs are cheap, so maybe some kind of switches with LEDs near them. I'm debating if the switches should even be part of the main circuit, I could just wire them on their own to turn the lights on and off and be a completely passive part of the display.If I could get a pretty small, cheap DVD player I could potentially wire it up to the LCD and have a microcontroller shoot a IR command to it to jump to a specific chapter that changes the background, sort of like going from a standard starry background to "hyperspace" and then back again. Or even just hot-wire in a switch to the chapter button.I'm probably going to get in over my head on this but I seem to do some of my best work when I'm in over my head.I think most of the smarts of the unit will be supplied by me via what I have on hand (microcontrollers etc) but we'll need to buy some switches and more LEDs and other parts to make it look neat.Parts I have immediately available:Code:ATTiny45 and 85(1 each)8 Pin PDIPATTiny2313(1 or 2)20 Pin PDIPATMega328P(3)28 Pin PDIPATMega324P(1)40 Pin PDIPATMega1284P(1)40 Pin PDIPMSP430G2553(3)20 Pin PDIPPIC16f627(1)18 Pin PDIPI/O ExpansionPCF8574(1)74HC595(3 or 4)Basic parts:Lots of diffused red LEDsMost values of resistors, and capacitorsLots of PN2222, 2n3904, 2n3906 transistors4 or 5 7805 regulatorsVarious wall-wart PSUsDev PlatformsArduino UnoMSP430 LaunchpadTI Stellaris LaunchpadTI TIVA C Launchpad (Basically same as Stellaris)TI C2000 Piccolo LaunchapdVelleman K8048 RS232 PIC ProgrammerPreferences:Stay with DIP chipsParts available from Tayda (cheap and quick to get)Parts from Tanner Electronics (not as cheap but I can drive there)Run from Internal OscillatorAny ideas for something that would look cool for some kids?

author: babysitter
author_rank: Frequent Contributor
timestamp: June 04, 2014, 07:44:09 am
content: Get 8 7-segment LEDs, at least one BCD-to-7-digit Decoder IC and 8 nice BCD wheel switches from ebay. Add counter and 555 for Multiplexing if desired. The number which is set to the wheel switches will be shown on the LED display. Scrap radio clocks might be a good source for LED displays.

author: old gregg
author_rank: Regular Contributor
timestamp: June 04, 2014, 11:02:03 am
content: for an aesthetic point of view, you can try to find out some dead old tube. SOme are really weird looking and could give a nice touch. Instead of LCD , why not this kind of display :It could be nice to introduce old unknown things to kids. I guess they're all accommodated with LCD/touch panel now.Just an idea !

author: EEVblog
author_rank: Unknown
timestamp: June 04, 2014, 12:29:23 pm
content: Someone has to post it, build one of these:

author: Stonent
author_rank: Super Contributor
timestamp: June 05, 2014, 12:56:46 am
content: This may deflate my options somewhat. My wife informed me after I ran some ideas past her that the display has to be able to be mounted to the pin up board using either thumb tacks or staples. Any parts that could be messed with can be covered with paper with the visible parts exposed.

author: thejamesclan
author_rank: Newbie
timestamp: June 05, 2014, 12:19:46 pm
content: Hi, you could use a 4 digit clock using 4 single large led panels that can be read by counting number of flashes. zero could be panel on.i.e 12:40panel 1 = 1 flashpanel 2 = 2 flashespanel 3 = 4 flashespanel 4 = on until <>0sequence could run through pretty quick and is a good counting exercise for the kids and eye catching. bi color leds could also be used to show active panel and a small micro and 32khz xtal should do the job and panels can be made to any design.Just thinking out of the box.

author: SL4P
author_rank: Super Contributor
timestamp: June 05, 2014, 12:46:27 pm
content: Maybe a large 6-digit LED display somewhere in the mix...Show real-time-of-day if no buttons for 30-secs. Kids won't wait 60 secs for the minutes to change.Keyword - INTERACTIVEAlso - 2 rows of 6 buttons (up & down) to set the displayed digits, then if untouched for 10 secs - start counting toward the real time of day. speed of count up/down based on distance from TOD. (blindingly fast -> fast to slower - eventually sync - and return to TOD display)Perhaps also soft-code the school bell times - and when the TOD reaches them - a strobe/lightshow with some sound (or a sound playback chip) makes an announcement.Maybe a slider or fader that causes some linear or other display/tone to interact. e.g. change brightness / color of LEDs, speed of audio playback...Stimulate the kids so thjey want to learn 'how'.Maye a servo driven circular temperature indicator - driven from temp sensor.Above all - paper won't protect anything anywhere with 8-9 year olds.Even vandal-proof buttons should be mounted on a plate that itself is very secure.LEDs will get pushed back through any openings - put perspex over the displays etc.Good luck - regardless of your direction - send photos of the build progress.(PM me if you want help coding (PIC or Arduino platforms.)

author: Stonent
author_rank: Super Contributor
timestamp: June 05, 2014, 12:49:15 pm
content: It will need to be completed by the third week of August either way. The school is about a 45 minute drive from where we live so I don't go there very often, but this weekend I may be up that way and get a chance to look at the area it might go.

author: madshaman
author_rank: Frequent Contributor
timestamp: June 05, 2014, 12:51:40 pm
content: Mini CRT(s) ? (Like a pull from a military display)It'd take some programming, and you'd be best off potting all the HV stuff (you're looking at <1KV acceleation voltage), but it could easily be driven from a uC.People make vector-based clocks out of them.

author: SL4P
author_rank: Super Contributor
timestamp: June 05, 2014, 01:49:02 pm
content: Further to my earlier suggestions - you can probably get almost everything you want (excluding CRTs etc) into a 20-25mm thick panel... height/width to be determined.If you use a rigid lightweight rear plate, (many) M3 x 20(25)mm threaded spacers and painted / silk-screened perspex front panel, this could easily hang from a couple of screws in the wall. using an external plug pack.Other ways to reduce weight are capacitive switches etc.

author: katzohki
author_rank: Frequent Contributor
timestamp: June 05, 2014, 01:56:17 pm
content: Man I remember doing the communities thing when I was in third grade. Half the kids opened up candy shops and I took home a 2 Litre bottle of soda with my profits!Being held up with pushpins does limit you a little bit I think, you wouldn't want something that could fall on a kid. The best idea might be something very simple:Make a clock run BACKWARDS! Whether that's an LCD, or some 7 segments displays or you hack up a cheapo analog wall clock (don't forget to double the speed at least!) is up to you. That just screams "Time Machine" in my opinion.After that, have the kids come up with the rest of the design and help decorate for it!

author: pdeboer
author_rank: Newbie
timestamp: June 05, 2014, 03:08:50 pm
content: How about using that LCD and a Raspberry Pi? Kids love Pi! Throw some rotary encoders on for year: month: day and a big engage button. Have the BTTF when you were, when you are and when you are going displays on the LCD and when the button gets hit it'll do some basic and hopefully free animation, possibly related to the time if you want to get intricate.

author: croyleje
author_rank: Regular Contributor
timestamp: June 06, 2014, 01:42:29 am
content: I don't expect it to be practical but Nixie Tubes would give it a great look that old Jules Verne theme. I also like the idea of an old CRT both ideas have readily available plans on line. Just a thought but way to fragile for kids.Jason

author: Stonent
author_rank: Super Contributor
timestamp: June 06, 2014, 02:13:08 am
content: I don't really want to tie up my RPi for this if I don't have to. The LCD I bought for about $5 so it's ok to use. Nixie tubes might cut in to the budget way too much. We probably don't want to spend more than about $20 to add to the parts I already have. Hopefully this weekend I'll start to play with some more ideas.

author: Rerouter
author_rank: Super Contributor
timestamp: June 06, 2014, 07:50:22 am
content: get a cheap analog clock with a quartz movement (almost impossible to not get) and mod in a little motor on the time set knob, so she can control with a potenitiometer or whatever how hast and in what direction the clock goes?you could add a 7 segment display on the bottom with year, (obviously you would speed up the rate at which the year changes vs the clock time) its nice and simple and most kids get the concept of a clock spinning backwards at high speed as being travelling back in time,

author: Stonent
author_rank: Super Contributor
timestamp: June 08, 2014, 08:25:03 am
content: We picked up two wall clocks today at a thrift store for a few dollars. My idea for running them forwards and backwards is to do a PWM signal with a fairly low duty cycle through an H bridge to go forward and then reverse it to go backwards. I should be able to speed up and slow down the frequency to control the speed.Anyway that's my theory. I'll probably need to put a diode in there to prevent any kickback from the coil from feeding back into the circuit and killing something.

author: Stonent
author_rank: Super Contributor
timestamp: June 22, 2014, 03:22:07 am
content: Update on the clock part, I've been able to drive the clock to spin by inverting the 2 pins every 18 ms. If I do it any faster, the clock will get stuck and just jitter.

author: SL4P
author_rank: Super Contributor
timestamp: June 22, 2014, 06:20:51 am
content: Great - send a short vid, it sounds like fun !

author: Rerouter
author_rank: Super Contributor
timestamp: June 22, 2014, 09:55:57 am
content: only issue with attacking the coil pins is it can only ever spin forward, which is why i suggested the time set knob,

author: Stonent
author_rank: Super Contributor
timestamp: June 22, 2014, 03:05:53 pm
content: Quote from: Rerouter on June 22, 2014, 09:55:57 amIt seems to randomly choose a direction... I'm uploading a video that a made several days ago.

author: Stonent
author_rank: Super Contributor
timestamp: June 22, 2014, 03:25:02 pm
content: The observations I'm making in the video are not "real" I made this video to share with some family members and confuse them.I think my clock is broken

author: katzohki
author_rank: Frequent Contributor
timestamp: June 30, 2014, 01:36:14 pm
content: I love it! Especially the reverse direction!

author: Stonent
author_rank: Super Contributor
timestamp: June 30, 2014, 02:42:31 pm
content: Last week I tried to get it to work from a 555, but looks like I need a +/- voltage input because the 555 was putting out a 0 to 5v square wave.Maybe I just need to see if there's a cheap chip that can turn 5V DC into +/- 2.5V AC

author: microbug
author_rank: Frequent Contributor
timestamp: June 30, 2014, 03:35:12 pm
content: The cheap chip you are looking for is called a capacitor.

author: Stonent
author_rank: Super Contributor
timestamp: June 30, 2014, 03:47:03 pm
content: Quote from: microbug on June 30, 2014, 03:35:12 pmWell I remember about reading you could use a capacitor to remove a DC offset but well I'm at 0 right now. I didn't think you could pull below 0 without something to pull to.

author: microbug
author_rank: Frequent Contributor
timestamp: June 30, 2014, 03:52:47 pm
content: See attached -- connect a capacitor in series with ground and the AC signal will become ground-referenced, i.e., 2.5V pk-pk.