Regulator from 12Volt to 6.8v

G'Day

I have a couple of batteries from old Power Guardians UPS which still read 13volts so I was thinking of using them via a regulator to power my GP3500.

Am I right in thinking I need to finish up with 6.8volts??

Any recommendations where to get it, on-line would be best?

About how much?

Thanks for any advice.

Waz

If your handy you could build your own with a kit from dick smiths or jcar for under $20

waznme wrote:G'Day

I have a couple of batteries from old Power Guardians UPS which still read 13volts so I was thinking of using them via a regulator to power my GP3500.

Am I right in thinking I need to finish up with 6.8volts??

Any recommendations where to get it, on-line would be best?

About how much?

Thanks for any advice.

Waz

Hi Waz

Yep you need to end up with about 6.8Volts. Like CJ said you can build one your self with a kit from Dicksmith or Jaycar

I did one like this.

Very neat and tidy Davsgold, you must be happy with your work.
Looks like there is a pot, middle just above coiled red wire.
Little difficult to see but is this regulator adjustable?

Cheers
Peter

G'Day again,

Thanks for that, I will check out Mr Smiths emporium next week when I go to town.

Adjustable would be better I suppose, I may get a different detector one day.

I guess this would only have to handle about one amp??

Waz

Hi Nightjar

Yes it works well, and there is an adjustable trim pot. Just remember that the higher the starting volts and the lower the finishing volts that there is more heat the be dispursed,

I don't use it anymore as I have a 4500 and use its own setup.

cheers dave

Hi Davesgold, Be careful is all I can say..most voltage regs .work fine if they... are made safe.. There is one that is what most power suppies are built on ... are a little more costly.. and dont get hot.. Its a LM2678 simple switcher high efficiency 5 amp step down voltage regulator..a google would give you a how to in sec...they are made by National Semiconductors... I was going to make one my self when I had the 3500..but have a 4500 now with a power supply to kill for...Good luck ..Bob..

Yep, the one I used was the ICI LM317 and it is attached to the cast aluminium box which acts as a heat sink. I used this on a GPextreme and it all worked fine. Now it all just sits in the cupboard.

Because, now I have a GPX4500 and use its battery and it certainly is a great piece of gear.

cheers dave

I,ve been using one of these Dick Smith plug in variable REGULATED car power supplies to power sd/gp detectors for 5 yrs {20 weeks detecting }now without hassle..capable of 1.5 amps { detectors draw 0.7 amp approx }...cost me $20....bought a spare but have not needed it yet....I plug it in to a 12v female connector {ciggy lighter type , $2.00 }which in turn is simply plugged onto battery terminals with spade connectors , adjusted the output to 7.5{7.7 volts actual } volts and glued adjustment dial in place , then ran the output through some diodes{40 cents each} to drop voltage to 7.1 volts. I then just wired this into the top of an old 6volt gel cell supply thus supplying the headphone jack and detector supply plug already wired up..This powers both machines with a smooth supply ..All in all , a small compact reliable setup so far.Fits in the backpack pockets easily...Small 12 volt batteries give about 4 hrs detecting and a 10 watt solar charger will charge a flat battery in about 3/4 hrs....With 3 or 4 small gel cell batteries in ya kit you should NEVER have power problems in the bush...Not as light as lithium but cheap as chips...

Ayounomad wrote:Small 12 volt batteries give about 4 hrs detecting and a 10 watt solar charger will charge a flat battery in about 3/4 hrs....With 3 or 4 small gel cell batteries in ya kit you should NEVER have power problems in the bush...Not as light as lithium but cheap as chips...

Is there any precautions needed with solar so as not to cook the battery. Or do you just connect it up? I am interested in getting a lithium battery set-up for sd2200.

Yes , of course without protection you must be careful not to cook battery , but they are pretty robust ..I just disconnect when above 13.2 volts..usually coincides mith my 3 hrs stints away from camp...Flat battery to over 13 volts in about 3 hrs in sunny conditions...I,ve had the same 4 batteries for 5 yrs now,,still working fine and holding charge....As a result of the detector power usage being about the same as the 10 watt solar panel charge rate , it is all very convenient...

G'Day

I was in Ipswich on the weekend so went to Jaycar and looked at voltage regulators.

The one that is variable from 3v to 12v is adjustable by 1.5v increments. Therefore either 6v or 7.5 so is this the one you people are recommending?

https://secure4.vivid-design.com.au/jaycar2005/productResults.asp?FORM=CAT AA0218

I imagine 7.5 is too much but would the 6 volt setting put out only 6 volts or is it more comparable to a 6volt battery (6.6v)

They did not have any that were infinitely adjustable and the assistant did not know much at all.

Or do I have to make one up from a kit???

Waz

Hi Waz

Yes a kit form and make it your self.

The one I used is a Dicksmith one, code no: K3592 and use a variable resistor (trim pot) for the variable fine voltage adjustment. Just put your multi metre on the out put side and turn the trim pot to the required volts.

Not sure which one in Jacar is the same, but the one you looked at would do if you had a variable resistor fitted in it in stead of the fixed jumpers.

cheers dave

Hi guys, was looking for the current that is drawn on a SD2100 running the 18"DD coil? Heard the maximum current draw on a SD2100 is around 800mA with a standard coil. I need to know this so I can get the correct 'resistor/trim pot' (variable resistor) to make this 'Voltage Regulator'.

V=7.3 I=800mA 7.3V/800mA = 9.125 Ohms
V=8.0 I=800mA 8.0V/800mA = 10 Ohms
Variable Resistor Pot = 9-10 Ohms

Is this correct anyone?
Anyone made one before?
Anyone know what pot to use?

Thanks 'GTR32'

Hi GTR32,
Just happened upon your post.
The trim pot they are taking about is a very small current, variable
resistor that adjusts the feedback resistance on the LM317 voltage
regulator IC, See the lower link). What you've worked out is what you'd
need if you used a series resistor, which is not the way to go about
it, but well done for thinking it out.

For instance 0.8 Amps through a 10 Ohm resistor will generate about 6
and a half Watts of heat, which is just wasted power. Even the LM317
will waste quite a lot of current through heating. The best way of
doing it is by using a switching regulator, which is very efficient if
well designed. A good design must incorporate good smoothing and
filtering so that the switching noise is not picked up by the detector.
Having a high operating frequency helps with this.

The old LM317 is OK if you don't have the knowledge to knock up a bucking reg.
Jaycar LM317 kit

Or you could make your own, this page shows how simple a three pin regulator can be
LT1084

A point to watch is that with an extremely Low Drop Out regulators (LDO
= minimum source Voltage the reg will still operate at) you could
discharge your battery below the end point Voltage and stuff it, but in
some cases depending upon your source it is better to get the best LDO
type available.

Good luck

I use a SD2100 and would like a lighter battery than the dometop. But having read (but not understood the technical bits) I wonder if these boxes are sold anywhere? ... I do enjoy a mystery and these type of topics are certainly that... but the more I read the more I understand
jt

I personally use an LM317 to get 6.8 Volts ,,supplied with an 11.1Volt Li-Po Battery,velcroed onto the side of my Extreme, making it cordless, (for power anyway.) , and have found this combination fantastic (and very light).
I used to use 2 x 7.4 volt li-po's in series(14.8- 16.4volt input) to feed it,(because of the 3 volt drop) and it definitely got hot, so i went for the 11.1 instead .
I even tried a LDO type regulator, Lm1117 (to use on standard 7.4volt batteries) but it was very noisy, since i believe i was exceeding its max of 800ma in power draw.
Maybe using 2xLM1117 in Parallel circuits might work.

Another option was just using a few power didoes (1n4001 or similar) in series with a 7.4 volt LIpo- Fully charged so the output didn't exceed 7.3 volts.
When the voltage drops to 6 volts, and the detector low battery warning sounds, you can then be sure that you haven't let the Li-Po's discharge too far since they will still be at 3.3 - 3.5 volts( 3.1- 3.2 volts is the danger level for them before damage occurs from over-discharging).

Best thing i ever did- getting rid of that heavy battery.