A question about alternative power supply for hp41 series

[walter b]

(02-27-2016 11:01 AM)wojtek Wrote:  The one named Marx will become related in history forever with his boy friend Fritz Angel (just kidding)
I supposed that "accu" was used in conversation between old surehand an old firehand during their visit at fake general's hacienda, but I can be wrong.

Thanks for the interesting biographic details. I didn't remember Old Surehand appearing in 'Winnetou' but I may be wrong.

c|:-)

[Dieter]

(02-27-2016 08:31 AM)wojtek Wrote:  ...10 year old Energizer with nominal capacity of 1800 mah and real probably less than 1000mah (I was afraid of damaging any of my eneloops).

You can avoid deep discharge by simply testing flag 49 in your program. If this flag is set, the 41's BAT annunciator comes on. You may check the voltage of your NiMH battery at this point to get the exact threshold. I once determined 4 V for a regular HP41 four cell battery pack.

Now imagine what you can do with a time module or a CX: store the current time at program start, check flag 49 at the end of each loop and if set exit, calculate the elapsed time and finally turn the device OFF.

Edit: A nice idea, but I just realized that this probably will not work here: If your DC-DC converter really provides 5,5 V even from an input voltage as low as 0,8 V this will not protect the battery from discharging to a level that is not recommended. But you may still find out at which input (!) voltage the 41 turns on its BAT annunciator. In other words: which input voltage of your DC-DC converter produces an output as low as, say, 4 Volts.

(02-27-2016 08:31 AM)wojtek Wrote:  Certainly if someone would like to apply such a converter to power the 41c it would be worth to invest in the newest eneloop of 2500mah capacity

These are the Eneloop XX/Pro with an extended capacily of typically 2550 mAh, but also with somewhat more self-discharge and a reduced number of charge/discharge cycles: 500 instead of 2000 (well, under perfect conditions in a smart charger). OTOH 500 cycles should be more than enough. ;-)

Dieter

[Dieter]

(02-27-2016 09:06 AM)walter b Wrote:  

• A 'false friend' in linguistics is called a term in a foreign language looking similar like a term in your native language but meaning something different. Some English examples for German readers: sensitive, handy, become, etc.

Hmm... did you possibly mean "sensible" when you wrote "sensitive" ?-)))

Dieter

[Jlouis]

(02-25-2016 02:26 PM)Artur - Brasil Wrote:  Just converting your words (I really would like to use HP50G solver):
t - time of continuous work [hours]: what we want to know
Cbat - battery capacity [mA.h]: let's say 2000mAh
Eff - converter efficiency [%]: 90%
Vbat - battery voltage [V]: 1.2V
Vcalc - operating calculator voltage: 6V
Icalc - operating calculator current [mA]: 10mA

So, using the solver for hp50g...

t[h] = Cbat*Eff.Vbat/(Vcalc.Icalc.100)

t = 36h of continue work;

Not bad, as I won't use it for so long time at once. Let's say, 1 hour daily -> easily 30 days.
Being less confident in numbers, I would say recharging battery once a week. Not bat, at all....

This if we don't put two AA batteries inside the battery holder - my mistake: really forgot to measure it yet.
And remember, we have stronger cell phone batteries available too.

Beyond calculations, what I really would like to express is this simple point: N cells here are difficult to find; I have some rechargeable, but thery are always depleted when I need them - and the charger is hard to find too... AA battery is easy to find (ready to use 1.5 alkaline or 1.2 NiMH, also easily chargeable).
so, its a question of hard x easy and also a new project to keep my mind occupied with something positive.

This is a very good post. Thanks.

[Jlouis]

(02-25-2016 03:14 PM)rprosperi Wrote:  

(02-25-2016 02:26 PM)Artur - Brasil Wrote:  N cells here are difficult to find

Here, Amazon has a set of 20 N Cells for less than $1.00 each, not expiring until 2019 (and they of course actually last longer). While shipping to Brazil surely adds to the cost, they are still pretty easy to buy and IMHO, pretty cheap.

Bob, that vendor doesn't ship to Brazil, and so others don't as well.

Even if we can find one, shipping cost and taxes ("only" 60%) makes it a little bit inviable, so I support Artur quest and hope he succeeds in his endeavour.

[Jlouis]

(02-25-2016 08:51 PM)Dieter Wrote:  Maybe these links can help:
Measuring Calculator Current PDF (cf. page 3)
HP41 Info data (search for "battery current")
Some more results in an older post on this forum.

Dieter

Thanks Dieter.

What a wonderfull thread.

Cheers

JL

[walter b]

Correct as usual.

d;-)

[Artur - Brasil]

For those interested in how I made my lateral connector and power supply for Hp41, please see the pictures.
Actually I didn't use one HP power supply for calculators. I got one small transformer (6+6/500mA), two diodes, one capacitor, one 6Vdc regulator and made the power supply.
From a power cable very common on mini-systems, I cut it and separate the two holes (female connectors) and inserted on them one piece of aluminium cut by myself.

Simple and works.

   
   
   
   
   

[Artur - Brasil]

I also received the step-up converter, but didn't have time to work on it...
My goal: put circuit and one AA battery (or in worst case, two AAA) inside the rechargeable pack. Allow to remove the battery for external recharging.
Let's see if I can do it this week!

[jebem]

(02-29-2016 01:11 AM)Artur - Brasil Wrote:  I got one small transformer (6+6/500mA), two diodes, one capacitor, one 6Vdc regulator and made the power supply.

Good work, Artur. Thanks for sharing.
Obrigado por compartilhar os resultados de seu trabalho.

From your pictures, I see that you chose to use negative common ground, so the regulator IC would be a 7806 or similar, right?

I can't see from your pictures, but I usually install a small value capacitor at the regulator IC output as well, to improve stability and bypass eventual RF noise.
One Tantalum capacitor with 3.3 to a maximum of 10uF is adequate in this position.
If Tantalum is not available, a regular small value electrolytic cap with a 0.1uF (100nF) ceramic or plastic RF capacitor in parallel will be adequate as well.

Also it seems that you are not using any heat sink with the regulator IC.
Does it get warm?
My guess is that it shouldn't, considering the extremely low current consumption of these 41C/CV machines (The bare machine, that is. If you start adding additional modules, specially a card reader, a substantial amount of current would be expected).

I can't retake current readouts from my 41CV as I'm not at home for a while, but I have some notes in my notebook that I took some time ago when I was restoring it.
For bare 41CV machine, it goes like this:
- Power Off state: 90uA (micro Ampere);
- Power Off to On sequence: 3.9mA;
- Key presses: 3.9mA;
- Power On idle: 0.9mA;
- Executing a program: 3.9mA

EDIT- Before I forget all the details on my readings (human brain memory can be tricky sometimes):
- All the mentioned readings were taken on a 41CV HalfNut;
- I just waited about 30 seconds to take each readings, so I didn't let the machine to settle down;
- The Power Off state current consumption was not steady (it drifted up and down wildly around that 90uA value) - this is most probably caused by one of the internal electrolytic capacitors and should considered as kind of "normal" considering the components aging. Also, 90uA leakage is probably lower than the batteries natural discharge rate.

[Artur - Brasil]

Great informations for my future dc-dc converter!
I'll make the improvements you told on my power adapter too.

Many thanks and follow the next news from the converter.

Artur

[Jlouis]

thanks Artur and Jebem!

Please, if it is possible, could you post the schematics and the specification of the electronics used (capacitors, diods, IC, etc)?

I have a CV [/align]and I'd like to built a power adaptor too!

Thanks again guys!

[Artur - Brasil]

Hi, Louis, are you brazilian? May I send you an email, as I believe it will be easier to explain how to make it. Many people here are pos-graduated in electronics, they already know the basics!
Artur

[Jlouis]

(02-29-2016 05:41 PM)Artur - Brasil Wrote:  Hi, Louis, are you brazilian? May I send you an email, as I believe it will be easier to explain how to make it. Many people here are pos-graduated in electronics, they already know the basics!
Artur

Yes Artur, paying my debts from past lives...

I will be very grateful, as I know only the basic of basics indeed...

Obrigado

[wojtek]

(02-29-2016 07:19 PM)Jlouis Wrote:  

(02-29-2016 05:41 PM)Artur - Brasil Wrote:  Hi, Louis, are you brazilian?

Yes Artur, paying my debts from past lives...

Why complaining? it is a beautiful country, you have over there quite a piece of woods, nice climate, warm all the time, no winters, nice beaches, Copacabana and first of all Brasilian festival with beautiful girls, so whats the problem?

[Jlouis]

(03-01-2016 08:37 PM)wojtek Wrote:  

(02-29-2016 07:19 PM)Jlouis Wrote:  Yes Artur, paying my debts from past lives...

Why complaining? it is a beautiful country, you have over there quite a piece of woods, nice climate, warm all the time, no winters, nice beaches, Copacabana and first of all Brasilian festival with beautiful girls, so whats the problem?

All you said is true. Come here, stay a few days, and leave (but take extremely care). Great. But there's no space enough and I don't want to bore fellows here with our huge problems. You may have an idea looking the news or searching with Google. But you will find find only the visible part of the iceberg.