Regulate 12V to 8.5 ???

[aufinda]

Hi Guys,
I'm not electronics savvy, and I want to regulate a 12V battery down to 8.5 V with enough current to supply a 4500.
Can anyone advise me of the simplest way to do this, please?
Cheers
Finda

[WM6]

You can use this regulator:

http://focus.ti.com/lit/ds/symlink/ua7808.pdf

according this scematic (put regulator on Alu cooling profile):

If you prefer to use capacitor occording datasheet then C1=0.33uF and C2=0.1uF.

Diode of course 1N4148 or other general use D, e.g. rectify 4000 serie diode.

[Mechanic]

Hi Aufinda,

The above example is the simplest way to do it. Make sure you use a heat sink on the lm7808, and make sure it is in the to220 or similar package. Is this for a detector if so what model.

Cheers Mick

[WM6]

If you sense more noise with this solution than usual with original battery, you can try to eliminate noises by use both proposed C2 (470uF and 0.1uF) together in parallel connection. You can do the same on input with C1.

And, sorry, small typing correction in schematic: not uC7808 but uA7808.

Also you can use 6V regulator (7806) instead of 8V (7808) if you cannot find last one. In this case you need to replace both 4148 with zener diode 2.5V (Remark: put zener cathode on opposite side as with 4148).

[IBGold]

Hi Aufinda,
You could if the electronics are a bit hard for you use a Dick Smith Kit No K3592 I change the LM317 to a LM350 and use a 470 ohm resistor in series with a 220 ohm potentiometer which will give you a variable regulator from 6.15 volts to 8.45 volts I have used this system for years with no problems on both SD2000M and GP3500M put it in a Die-cast box and use that as the heat sink and away you go hope this helps.
Regards,Ian.

[aufinda]

Thank you all very much guys, some I think I could manage some I have doubts about, however, I found this on ebay, what do you think

Cheers
Bill




http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=300436899301&ssPageName=STRK:MEWNX:IT

[Aziz]

Hi Bill,

the switch mode power supply (SMPS) could be quite noisy as it's clock frequency is not synchronized to the detectors operating frequency.
In case of it is very noisy, you can use a low drop out regulator L4940V85. It delivers 8.5 V output at 1.5 A current.

L4940V85
http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXwrwq.pdf

You can put a 9V input and it still can regulate to 8.5V output.

Aziz

[WM6]

Thank you all very much guys, some I think I could manage some I have doubts about, however, I found this on ebay, what do you think

Cheers
Bill

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=300436899301&ssPageName=STRK:MEWNX:IT

Good one, take it.

Aziz thanks for info.

[aufinda]

Hi Bill,

the switch mode power supply (SMPS) could be quite noisy as it's clock frequency is not synchronized to the detectors operating frequency.
In case of it is very noisy, you can use a low drop out regulator L4940V85. It delivers 8.5 V output at 1.5 A current.

L4940V85
http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXwrwq.pdf

You can put a 9V input and it still can regulate to 8.5V output.

Aziz

Thanks Aziz,javascript:replaceText('%20::62::',%20document.forms.postmodify.message);

I actually want to regulate 12v to 8.5 for my 4500

If I have to use the regulator you suggest above, do I have to make up a small circuit "circuit parameter"
as shown in the above reference, or can I use the regulator on its own? (I don't know anything about electronics), and...

Is 9V too much to feed into a 4500?...because there is a 12V LI-Ion already regulated to 9V available .

Cheers

[Doug]

Hi Bill,

the switch mode power supply (SMPS) could be quite noisy as it's clock frequency is not synchronized to the detectors operating frequency.
In case of it is very noisy, you can use a low drop out regulator L4940V85. It delivers 8.5 V output at 1.5 A current.

L4940V85
http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXwrwq.pdf

You can put a 9V input and it still can regulate to 8.5V output.

Aziz

Thanks Aziz,javascript:replaceText('%20::62::',%20document.forms.postmodify.message);

I actually want to regulate 12v to 8.5 for my 4500

If I have to use the regulator you suggest above, do I have to make up a small circuit "circuit parameter"
as shown in the above reference, or can I use the regulator on its own? (I don't know anything about electronics), and...

Is 9V too much to feed into a 4500?...because there is a 12V LI-Ion already regulated to 9V available .

Cheers
Billjavascript:replaceText('%20::98::',%20document.forms.postmodify.message);

I don't know what is going on with the javascript messages in your post.
I have never seen it before in any forum messages so i am at a loss to explain it!
doug

[Doug]

Hi Bill,

the switch mode power supply (SMPS) could be quite noisy as it's clock frequency is not synchronized to the detectors operating frequency.
In case of it is very noisy, you can use a low drop out regulator L4940V85. It delivers 8.5 V output at 1.5 A current.

L4940V85
http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXwrwq.pdf

You can put a 9V input and it still can regulate to 8.5V output.

Aziz

Thanks Aziz,javascript:replaceText('%20::62::',%20document.forms.postmodify.message);

I actually want to regulate 12v to 8.5 for my 4500

If I have to use the regulator you suggest above, do I have to make up a small circuit "circuit parameter"
as shown in the above reference, or can I use the regulator on its own? (I don't know anything about electronics), and...

Is 9V too much to feed into a 4500?...because there is a 12V LI-Ion already regulated to 9V available .

Cheers
Billjavascript:replaceText('%20::98::',%20document.forms.postmodify.message);

Does the 4500 have an internal voltage regulator? If so then any input voltage above this regulated voltage will be a waste and of no benefit.
doug

[aufinda]

Hi Doug,

I tried to drag an couple avatars onto the message, I probably did the wrong thing.

Re the 4500, I'm not sure, I think it may be internally regulated, I'm not looking for any advantage by putting in 9V, it's just that there is a 12V battery that is regulated to 9V available, and I'm wondering if it would do any damage to the machine if 9V was supplied instead of 8ish V?

[Jumbo]

Aufinder...
                I played with a 12volt variable regulator on the 4500, applying 9volts brings up the message on the screen "Overvoltage shutdown" and shutdown follows!
Jumbo

[aufinda]

Thanks Jumbo, that answers that question.

Out of interest, did you end up finding out what the upper acceptable voltage was?

Cheers Mate

[Aziz]

Thanks Aziz,

I actually want to regulate 12v to 8.5 for my 4500

If I have to use the regulator you suggest above, do I have to make up a small circuit "circuit parameter"
as shown in the above reference, or can I use the regulator on its own? (I don't know anything about electronics), and...

Is 9V too much to feed into a 4500?...because there is a 12V LI-Ion already regulated to 9V available .

Cheers
Bill

Hi Bill,

yes you would need a small circuit just as specified in the data sheet. You would need some capacitors and if your input voltage is high (12V), then additional a heat sink for the voltage regulator. Note, the voltage difference of input and output will generate heat only (waste of energy). Using a low drop out (LDO) regulator minimises the energy loss and they accept lower input voltages (9V).

The standard 7808 regulator needs at least 2V higher input voltage. But the LDO L4940V85 has less than 0.5V voltage difference. So it can be operated at 9V.


Switch mode regulators (SMPS) usually convert almost all of the energy of the battery into the required output voltage. The energy loss is less compared to linear voltage regulators. But they are switching coils at high currents and frequency and they can disturb the operation of the metal detector. So a synchronisation of the SMPS to the metal detectors pulse frequency is very important.

One have to try it out, if a specific SMPS will run with a metal detector. If it does not generate much noise, than it is the preferred configuration due to high efficiency.

Aziz

[aufinda]

Thanks Aziz, I'll wait ans see how the one I've ordered goes, never know it may be OK.

Thanks for your help mate.

[greygoose]

I have bought an LM2596 DC converter off E Bay to make a battery Pak.
Where do I go from here?. I am not that knolegeable electronically. Do I use NiMh Batteries If so how many and how wired for GPX 4000.
Is there a made up pak I could use. Any advice would be greatly appreciated.

[Mechanic]

Hi Greygoose,

You would be better off staying away from the regulator/dc/dc converter as this will add extra noise, we are dealing with a precision measurement instrument(metal detector) so we want things as quiet as possible.

You can get camera batterys off ebay, for a canon bp70g. There are cheap chinese ones and there are cheap ones with japanese cells, which are the good ones. Not all of them come with chargers, so be aware that you will need to get a charger.
http://shop.ebay.com.au/?_from=R40&_npmv=3&_trksid=m570&_nkw=bp970+battery
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200562213521

However, you will still need to carefully pull this battery apart to bypass the protection cct for running the detector as the cct will fail with the high currents the detector uses. You still leave the protection cct there and connected so the battery is protected during charging. So you ned to then hook up a wire to the output of the battery and make sure you use a 1.5A thermal breaker as close to the battery as possible, as this protects the battery and equipment if something shorts out.

You may also need to put a diode in series with the battery to drop the voltage if the detector does not want to fire up because the voltage is too high.

Be very careful when you do set up something like this, don't short out the battery while your working on it and be sure that you have the voltage connected up correctly before connecting to the detector!

Cheers Mick

[greygoose]

Thanks Mick

I will stay away from it. I think I have wasted $5.00.

Cheers Sid.

[Mechanic]

Hi Sid,

Keep it for a rainy day! You may want to regulate voltage for something else at some stage.

I have a whole box of parts that I have purchased over time for whatever reason, but decided not to use for whatever reason, occasionally they do come in handy when I blow something up or am fixing something!

Have fun and welcome to the forum...

Cheers Mick