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I'm thinking of powering each of the calcs I test with an old AC/DC converter I got from my dad(so as to avoid putting fresh batteries in every single one), and while I know to set it for 6 volts(4x 1.5v AA) I need to know how many amps a calc needs to function, and how many would be too much, so I don't break them myself.
14 billion watts.
I'd be seriously surprised if it ever draws more than 100mA or 200mA. The peak current will be when it is writing (or rather, erasing) the Flash chip, but even that is current-pumped.
This may not be such a great idea as most "wall wart" power supplies are unregulated and will output a far higher voltage than the selected one with low loads. At the very least use a L7805 between the PSU and the calculator to regulate the voltage to a clean 5V (as the calculator operates fine on rechargeable batteries - i.e. 4.8V - you should be safe with 5V).
benryves wrote:
This may not be such a great idea as most "wall wart" power supplies are unregulated and will output a far higher voltage than the selected one with low loads. At the very least use a L7805 between the PSU and the calculator to regulate the voltage to a clean 5V (as the calculator operates fine on rechargeable batteries - i.e. 4.8V - you should be safe with 5V).
An excellent idea, I would do the same. In fact, back in the day I had something that I think I called Multidock or something? No, it's was MultiNet. Anywho, it was a design for a port on the calculator and a corresponding dock and plug to disconnect the batteries and feed the calculator regulated power when docked. I should try modding my current calculators so I don't have to keep buying 48 AAAs at a time.
I forgot the M in LM7805.

USB is another good source of regulated 5V DC and can supply up to 100mA by default.
benryves wrote:
I forgot the M in LM7805.

USB is another good source of regulated 5V DC and can supply up to 100mA by default.
Eh, I knew what you meant about the voltage regulator. Wink Actually, I think it would be a good idea for me to at some point put an ammeter in series with my calculator's batteries and figure out how much current it draws doing various things.
KermMartian wrote:
I'd be seriously surprised if it ever draws more than 100mA or 200mA. The peak current will be when it is writing (or rather, erasing) the Flash chip, but even that is current-pumped.


This ^. Be careful not to make the calc asplode Razz
Definitely. Smile I was quite surprised the first time I tried to measure the voltage of a wall wart-type supply with no load connected and found it not only around 150% of the rated voltage (around 18V for a 12V supply, if I recall correctly) but also quite noisy and dirty.
well this is an AC/DC converter for use with simple electronic experiments so it's probably pretty stable, but I also have a USB bluetooth charger I could possibly use.
DShiznit wrote:
well this is an AC/DC converter for use with simple electronic experiments so it's probably pretty stable, but I also have a USB bluetooth charger I could possibly use.
Do you mean a wall wart, or a more complex regulated circuit? If the former, it's very undependable. If the latter, could you point us to details?
It's not a wall wart, but I need to dig it out from under a pile of electronics before I can give you any more detail.
DShiznit wrote:
It's not a wall wart, but I need to dig it out from under a pile of electronics before I can give you any more detail.
Very good, I look forward to the details. If it's some kind of bench power supply, then we can expect it to be somewhat more reliable in terms of output consistency.
Crap, it wasn't in the box I thought it would be in, but I did find a wall wart for charging the Nintendo DS Lite if that can work? Otherwise, how do I do this with USB?
DShiznit wrote:
Crap, it wasn't in the box I thought it would be in, but I did find a wall wart for charging the Nintendo DS Lite if that can work? Otherwise, how do I do this with USB?
USB gives you clean, 100mA power over the red and black wires; white and green are data, so you don't want to touch those. The way the batteries are arranged in the calculators, with the back up and the top edge of the calculator away from you on a table (TI-83+: link port towards your chest; TI-84+: link and USB ports away from you), the lower-left contact is the main +, and the lower right is the main -, which you can confirm with the battery markings under the batteries. You would connect red to + and black to -, feeding in 5V where it expects 4.8-6V, so it should be happy enough.
Awesome, I'll give this a try when I get home.
DShiznit wrote:
Awesome, I'll give this a try when I get home.
Just make sure you don't get the power from something valuable, like a computer, in case you short something by accident. Do you have any power supplies with a USB socket? Or perhaps a powered USB hub? Also, if you have a multimeter, it would be great to check the voltage before you connect your calculator.
I know BrandonW has built or was at least looking into powering a calc with USB for his calc over the internet project and I'm sure its viable to do.
TheStorm wrote:
I know BrandonW has built or was at least looking into powering a calc with USB for his calc over the internet project and I'm sure its viable to do.
It's very viable and easy, as per what I was discussing above. Smile It would be even nicer to tap the USB socket inside your trusty TI-84+/SE calculator to power it.
Please forgive the crudity of this model, I didn't have time to paint it or build it to scale:
  
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