Voltage multiplier

[ivconic]

There are vintage detectors that use many batteries and higher voltages.
For example i would take Cscope 1220B.
It has 2 packs , each one for 6 x 1.5v (or 1.2).
At the end it is 2 x 9v (or 2 x 7.2v if rechargeable).
But actually it is 1 x 18V (1 x 14.4v), because those packs are connected in series.
However, 1220B actually need 13v to operate by defaults.
I was tried even with 12v accu and it is working the same, i haven't spotted any changes in behavior.
So... it will work nicely in range 12v to 18v with no problems.
It's battery compartment is large enough to hold one 6v gel accu.
So i made voltage multiplier and tested it. Working just nice.
No problems at all.
Cscope can draw current from 17mA (with no detection, in all modes) to ~50mA (with loud sound at single tone modes) up to 150mA (at VCO audio mode when detection audio is extra loud).
So... i checked behavior with this voltage multiplier.
I get pure 16v at multiplier output without 1220B attached on it.
Than there is 15.85v when 1220B attached and switched ON.
In single tone modes at 1220B with loud audio i measure 13-14v at multiplier output.
In VCO audio mode at 1220B with extra loud audio than it is 11V at multiplier output.
Last one is not a problem, because in real life, when prospecting, it is rare case to step on such large item in soil, which will produce such loud and strong response at 1220B.
Especially when earphones are used, than power drain can not reach mentioned 150mA but barely 80-90mA.
So... problem solved.
From now on i will use only one 6v battery. Rechargeable, of course.

[ivconic]

Schematic...

[ivconic]

Also found another one which is interesting to me:
(maybe will try this one too)

[johnandles]

Hello, I have old garrett vlf/tr that uses 6 x 9v accu,I wish to seperate coil and handle from control box.(to make it lighter)
Maybe I could mount accu in new box attached to the handle coil assy to assist balance.
the voltage for vlf/tr is 4x9 =36.
The audio is 2x9 in parallel =9volt.
any idea how to achieve this.
I would like to make voltage doubler and use nickle metal hydride accu.
thankyou for any suggestions.
john

[ivconic]

First you have to do is to somehow obtain it's schematic.
Analyzing it we can dig out how to modify it and adapt for use with less voltage... or at least with less batteries.
6x9V is really MUCH! What were they thinking?
I bet it can be modified to work with just one accu, at least one 12V gel.
But first we need to see schematic.

[ivconic]

I just looked at my files, Garret Master Hunter Deepseeker is having also 6x9v !

[ivconic]

...

[ivconic]

Actually, you need 15V for detector to work properly.
They "boosted" it up with 36V because of the voltage drop. (those 9v batteries are really poor and short lasting)
I don't see the point?
You can use my schematic from the post No1 from this page.
You will get 16V with it.
For audio part (2x9v in parallel) you put 7809 voltage regulator, across those 16V and that's how you will supply it.

[ivconic]

johnandles, here is possible solution for your Garret:

[ivconic]

Keep in mind that battery check/test will not work properly in this case.
But who cares?
As long as your Garrett is supplied properly and working good.
At my 1220B also battery check is not showing the reality, because internal components are chosen to match 18V battery voltage.
Now with 11-16v it is always indicating "low battery", yet it is working just nice.
Same will be in your case.
To match this; we should recalculate come components values at battery checking stage.
Trivial job.
I gave up of doing the same at my 1220B.

Simply because that gel cell battery 6V will provide enough power for hours and hours of proper detector functioning.

[ivconic]

Second look...
Here is where you gonna connect 16V supply from voltage multiplier.
Also power On switch must be rewired so to switch ON and OFF that wire instead point at 47 ohms at 2N3904 collector.
So 2N3904 with including components will be "by passed" and out of functioning.
2N3904 and first half of LM358 and surrounding components are there to regulate 36V down to 15V.
So, by bypassing them you will void voltage drop and get pure 15(16)v there.
Further, 15v are divided to +7.5 and -7.5 volts which are supplying the detector circuitry.
Apart the audio stage, the rest of electronics is not drawing much of a current, so i am sure that voltage multiplier will provide much more than enough power for it.
Audio stage may draw some descent current, but in most of the cases it will be in ranges that voltage multiplier can easily take. No worries about that.

[bernte_one]

18650

hello ivconic

have thought about to use 18650 akkus (LiIon)
you can buy them as single cells or cut them out from some uses notebook cells
a charger you can buy from dealextreme or something else
a holder for the akkus you canget here http://www.virtualvillage.de/5x-batt...06310-012.html
or build them self with some piece of pipe and some contact

could save some weight

[ivconic]

Even easier and better:
This is how you will void rearranging the main switch...

[Qiaozhi]

hello ivconic

have thought about to use 18650 akkus (LiIon)
you can buy them as single cells or cut them out from some uses notebook cells
a charger you can buy from dealextreme or something else
a holder for the akkus you canget here http://www.virtualvillage.de/5x-batt...06310-012.html
or build them self with some piece of pipe and some contact

could save some weight

Have you given any thought to a suitable charger for Li-ion batteries?
Of course, I mean a DIY version.

[ivconic]

hello ivconic

have thought about to use 18650 akkus (LiIon)
you can buy them as single cells or cut them out from some uses notebook cells
a charger you can buy from dealextreme or something else
a holder for the akkus you canget here http://www.virtualvillage.de/5x-batt...06310-012.html
or build them self with some piece of pipe and some contact

could save some weight

That could be also nice solution.
Yet, as a dedicated and persistent prospector, i don't trust much at such small batteries! (old school!)
There are frequent cases when i spend 10 and more hours on the field, prospecting and coinshooting.
Gel cell batteries (accu's) so far turned to be only possible solution for me!
I do recharge it fully at home and later i am calm and have no worries.
But in case you are not planing to use detector on the field for more than just hour or two - than such smaller batteries are excellent solution for you.