Multi Expansion Project

[DigiTan]

Well, I finally finished the first half of my TI-82hardware mod project. This half includes a power source expansion that gives the calculator 2 new sources of energy. With the current setup, the energy supply is estimated to be 300% greater for "Heavy Duty" batteries and 318% greater for Alkaline cells.

Current Features

Primary Power
This is a wall adapter supply. The adapter plug goes into the front of the box. A power switching relay isolates this circuit from the rest of the calc whenever external power is not present. The box can draw energy from virtually any 5.62mm (right size?) wall adapter (center-positive). The high current availbilty totally eliminates screen ficker. A yellow LED indicates when the calc is receiving external power.

Secondary Power
The Ti-82 now uses AA batteries for secondary power. The incresed current from these cells also decreases screen flicker, and seems to improve the calc's speed slightly. Since there's are 2 battery packs now, you can swap out one set of batteries without turning off the calc. This battery pack is bolted to the bottom of the calculator.

Auxillory Power
These are the normal AAA batteries.

Other Changes
A link port has been placed on the front of the box. The original 2.5mm link port was removed. A 3.5mm port has been added to supply power and data for external add-on circuits (reading light, IR link, etc).

Design Limitations
* Have to turn off calc before plugging/unplugging the adapter (to avoid an auto-reset)
* The battery packs aren't fully isolated (energy waste)
* The voltage drop across the circuit makes the batteries seem "deader" than they really are.

Future plans

The final half of this project will include an external 512KB Flash ROM. The ROM is partitioned into 9 "pages" that can hold variables, group vars, or backup files. The memory pages are LED color coded (green-green, green-orange, green-red, orange-green, etc).

[DarkerLine]

Can you post a picture?

[DigiTan]

I'll post them as soon as I can get my hands on a digital camara. It looks very "suped up." Does Kinkos have a photography section?

[jtchange]

sounds very interesting. Maybe someone who has the time could even 'port' it or create it off of ur idea for the ti83 series. that would be awesome since i own a ti83

[DarkerLine]

What would really be cool is a color screen. Maybe a second, transparent screen that could be accessed only by an assembly out instruction?

[DigiTan]

Well, I finally tested it at school today. I had it plugged into the wall for almost 3 hours with no smoke, toxic fumes, or explosions. That passes my test! I had some trouble with "battery mode" due to a loose/dead battery, but I guess that's a minor problem. Right now the estimated battery life is 25 hours, 55 minutes. Sweet! I'm going to start rounding up the plans to publish them at ticalc. Pictures will come as soon as I can find a camara...

[X1011]

How would you make a "flash ROM" for the 82, i thought it didn't support that.

[DigiTan]

It's more of an external archive, as I like to call it. The basic idea is to send backup files and vars to the external ROM though the link. It's just like transfering stuff to another calc, really. I'm limiting the ROM size to 9 pages to simplify the interface (1 button and 2 LEDs). The tricky part will be "fooling" the TI-82 into sending/receiving files. But it's been done before.

I'm beginning to install my video camara drivers. Pics are coming very soon.

[NextPerception]

This sounds like a pretty cool project you have going.
It sounds great for a person not worried about reducing the portability of the laptop.

[Tyler]

**//Months Later\\**

Pictures??

[DigiTan]

Ack! They're coming they're coming! I've been going back an forth with Tech support for the past few days trying to replace the camera drivers my roommate lost. They tried to send me the zip file tuesday, but the campus mail server stopped it! They sent it to my mom's email, so I'll probably have them posted saturday.

In other news, I'm going to order the Flash chip this weekend. Because of the chip size, I'll need to custom-etch a circuit board this time. I things go smoothly, the full project will get finished this May.

[DigiTan]

Okay. Here are the pictures of the current design. The picture quality is a bit grainy but it gets the point across. Note that because of the shadows in the room, both the black battery box and the gray Multi Expander box appear larger than normal.

This is the calculator in normal operation. From this angle, you can see the 5 multicolored power/data lines that enter the TI82 through the former link port. Also notice the 9v AC->DC adapter behind the calculator...



This is the calculator running off external power. Notice the power indicator LED is on now, and the power cable enters from the front of grey box...

[DigiTan]

Here is the bottom of the Secondary power bank with the battery cover removed. With both battery packs running in parallel, even my cheap Dollar General-brand batteries deliver enough kick to keep the screen nice and dark..



The three modular ports. Going from left to right, you have the 3.5mm port (general-use +6v supply), wall adapter port (center-positive), and 2.5mm (calculator link). Future enhancements (IR link, LCD clock, etc) will plug into these modular sockets...

[Bluefire]

sERIOUSLY, IF U CAN GET THAT TO WORK FOR THE TI 83 PLUS, ill pay money, ill send u my calc and say hook it up because that is AWESOME :lol:

Or at least let me buy a kit with full instructions from you!

[Adm.Wiggin]

that rox dude

[DigiTan]

Well, its not quite fully optimized so I wouldn't feel right profiting from it yet. The parts it uses now are mostly "general-purpose" components, so they get the job done but there's still lots of inefficiency. But I'll start working on a "kit" tutorial for ticalc.org this week.

[NextPerception]

I like the idea of were the battery placment was

[Arcane Wizard]

[DigiTan]

It's getting there. I'm still trying to find the best components to use in the "battery mode" circuit. So far I've been using general-use parts. They work ~okay but they waste a little more power than I expected earlier.

[Blackwolf189]

i am very interested in learning to do things like this however i can not take an electronics class until i am a junior and i am currently a freshmen. are there any websites or books that u recommend for learning electronics online. i have already begun searching for myself. A post of tutorials would be good for newbies such as me.