> I have an hp2621a terminal which had a battery to keep nonvolatile settings
> (eg baud rate, parity &c). I want a chargeable battery to keep those settings
> going but to charge when I have the machine on.

The issue that comes to mind is whether a/the power-supply would cause problems if connected to the terminal with or without the battery. If not, would an appropriate Zener diode do the trick?

Peter Wieck
Melrose Park, PA

In <07c6dfdb-88a5-4441-8e85-c7a0ee43bfcfn@googlegroups.com> by Peter W. <peterwieck33@gmail.com> on Fri, 17 Mar 2023 10:23:27 we perused:
*+-> I have an hp2621a terminal which had a battery to keep nonvolatile settings
*+-> (eg baud rate, parity &c). I want a chargeable battery to keep those settings
*+-> going but to charge when I have the machine on.

*+-The issue that comes to mind is whether a/the power-supply would cause problems if connected to the terminal with or without the battery. If not, would an appropriate Zener diode do the trick?

Thanks..

THough I also realise I could get two batteries, use one, charge the other..

But I suspect it will not fit exactly so I need to solder it

--
Vasos Panagiotopoulos panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---

On Friday, March 17, 2023 at 2:13:50 PM UTC-5, vjp...@at.biostrategist.dot.dot.com wrote:
> In <07c6dfdb-88a5-4441...@googlegroups.com> by Peter W. <peterw...@gmail.com> on Fri, 17 Mar 2023 10:23:27 we perused:
> *+-> I have an hp2621a terminal which had a battery to keep nonvolatile settings
> *+-> (eg baud rate, parity &c). I want a chargeable battery to keep those settings
> *+-> going but to charge when I have the machine on.
>
> *+-The issue that comes to mind is whether a/the power-supply would cause problems if connected to the terminal with or without the battery. If not, would an appropriate Zener diode do the trick?
>
> Thanks..
>
> THough I also realise I could get two batteries, use one, charge the other..
>
> But I suspect it will not fit exactly so I need to solder it
> --
> Vasos Panagiotopoulos panix.com/~vjp2/vasos.htm
> ---{Nothing herein constitutes advice. Everything fully disclaimed.}---

Just another point, although it is basic- Be extremely careful when you do solder!
HEAT from any source including soldering can create adverse conditions or
effects. If you have multiple batteries, gang them in a wrap with the contact points
exposed at either end (if the batteries are stacked) in order to minimize the points
at which you solder. Also, solder momentarily in a relative sense. That way, you
minimize contact time, still perform the task, and get an effective connection that
will adhere in the process. Whatever you do, be extremely aware and be very
careful. There is some risk involved in doing this and wear eye protection.

Best wishes.

Charles Lucas

On Fri, 17 Mar 2023 12:45:45 -0000 (UTC),
vjp2.at@at.BioStrategist.dot.dot.com wrote:

>How do you use diodes and capapcitors to switch a 4v power supply
>so it continuously charges a battery when not being used.

First, you must specify what type of battery chemistry we are talking
about. But I can't imagine doing it with just diodes and capacitors.

>keep nonvolatile settings

Depending on your specific application, a super capacitor might be an
option?

How do you use diodes and capapcitors to switch a 4v power supply
so it continuously charges a battery when not being used.

I have an hp2621a terminal which had a battery to keep nonvolatile settings
(eg baud rate, parity &c). I want a chargeable battery to keep those settings
going but to charge when I have the machine on.

Decades ago someone posted how to have a bike generator charge a capcitor so
that when you brake, you can power a back red light.

--
Vasos Panagiotopoulos panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---