minelab voltage regulator

[dave]

i have a minelab sd 2100 and i want to increase the input voltage from 6 volt to 7.8...they are finding that these detectors run smoother and go deeper at this voltage...can anyone tell me how to build an adjustable voltage regulator for it...my input voltage will be around 8.4 volts...i need a reliable adjustable regulator that will keep it around 7.8 volts...also can anyone tell me how to build an audio amp for a detector...these minelab detectors dont sound off very loud...thank you

[Goodrat]

Re: minelab voltage regulator

Don't you mean the "output" voltage of the regulator? It is probably a 5 volt and can be increase with a diode in series with the regulator ground pin. This would give you about 5.7, but I would not try it.
But maybe the situation is that the 6 volts is not enough to keep the output at 5 volts as the batteries die?

Maybe you should try better phones for the volume probem? Have you tried Ratphones?

[dave]

Re: minelab voltage regulator

yes..i'm sorry...i meant output voltage...austailain minelab guru's do upgrades on these detectors....and i've found out that all they are doing is increasing the voltage.....instead of 6 volt...they use 12 volt and regulate the voltage down to 7.2...as far as head phones go....the problem isnt that the detector doesnt have volume control..its that they just arent very loud...most people have to buy audio amps just to hear them

[Carl-NC]

Re: minelab voltage regulator

I believe the older Minelabs did not use a regulator... the circuit was powered directly by the battery. Therefore performance falls off as the battery drains. A common mod is to use a larger battery with a regulator.

- Carl

[Carl-NC]

Re: minelab voltage regulator

I recall that 7.2 volts or so was the recommended maximum. You might want to check this.

Also, 8.4v only gives you 0.6v of drop-out to work with (at 7.8v out), and that's not much at all. If you want to stick with 7.8v, I would suggest a higher battery voltage.

There are lots of adjustable regulators out there, but you really need to know how much current is needed. I would put, say, a 0.1 ohm resistor in series with the battery and look at the voltage drop with an oscope. This will give you the peaks. If you don't have an oscope, use a voltmeter, which will give a time-averaged value.

Once you know the current needed, select a regulator that can handle that amount, and has a reasonably low drop-out voltage. The phenomenally popular LM317 probably can supply the current, but has an abysmal 1.5-2 volt drop-out voltage. This comes right off the battery, so for 7.8v, you need a minimum battery of 9.8v, plus whatever discharge curve you need. So probably a 12v battery.

One nice thing about an adjustable regulator, is that you can give it an adjustment knob to vary the output between, say, 6v and 7.8v. Which effectively varies the detector depth.

- Carl

[dave]

Re: minelab voltage regulator

hi carl....i talked to a tech at minelab..he said the 2100 pulls 700 milliamps

[Goodrat]

Re: Volume

What is it with Minelabs not being loud enough? All of them? Is the output a 5V square?

[dave]

Re: Volume

all of the sd series have low volume