Omnimaga
Calculator Community => TI Calculators => General Calculator Help => Topic started by: GuyRobo on May 06, 2013, 05:35:19 pm
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I am new to this site, so if this topic needs to go somewhere else, please let me know.
I am looking to make a frontlight (instead of backlight) for my TI 84+SE. I have already made the light and it's stand/base and make it so it directly wires into the USB port through a miniUSB plug. The LED runs on 4-6 volts, so I thought It would work fine.
But the USB port does not send out the 5v I was looking forward to. Is there some program that will force the voltage out, or is it more applicable to wire the USB port directly to the batteries by opening up my calc? If I have to do the last one, how do I open my calc up?
Thank you in advance.
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The TI-84+/C/SE uses a linear voltage regulator to drop the voltage coming out the batteries down to 3.3 V. Then, inside the ASIC, it uses a charge pump to boost the voltage back up to 5.0 V. That charge pump is not active most of the time. You'll need an assembly program to turn it on. It would be unwise (though probably harmless) to attempt to connect the calculator to a computer when the charge pump is active.
Do not attempt to wire the USB port directly to the batteries. Doing so could damage anything you connect to the USB port. If you're willing to disassemble the calculator, it would be better to cut a hole in the calculator to make your own port for the light. Though, by then, you might as well just make it a traditional backlight controlled by a switch.
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The problem with a backlight is that you have to separate the LCD from the metal piece which is not easy and you risk damaging it.
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If you really want a backlight that much, you could also buy a TI-84+CSE. . . .
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The I/O linkport outputs 3,3V. Try hooking it up to an external charge pump circuit and let that drive the LED. How many miliamps do those LED's need?
(http://www.talkingelectronics.com/projects/50%20-%20555%20Circuits/images/VoltageDoubler.gif)
This relatively simple circuit doubles the input voltage. It can supply up to 50mA as long as the source can keep up.
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If you really want a backlight that much, you could also buy a TI-84+CSE. . . .
It probably depends if he wants to deal with slower speed, though :P (although it's only really bad if he types stuff but need to modify it or for editing large programs, but otherwise it's not that bad). The problem with a 83+/84+ backlight is if not done properly, then it won't look pretty. The Casio FX-9860GII calcs, which use an LCD similar to older models, but have a backlight, do a pretty good job. However, from hardware modders, I did see some horrible 83/86 backlights before, like at , but I saw some that are kinda good, like
Welcome here by the way GuyRobo! :) We also have an hardware modding/technology section on the forums, but it's located outside the calculator sub-forums since it's not specific to calculator modding, unlike here http://www.omnimaga.org/index.php?board=145.0
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You could also use USB8X to put the USB port on 'power only' mode, which will make the USB port output 5V.