Calculating current draw on my Pro-652

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vernongt

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G'day all,
In the user manuals of all my Pro-163/164 scanners, the specifications indicates the radio draws 200 milliamps.
This Pro-652 does not indicate.

Because we live Off-Grid [solar power & batteries], I like to know just how much each electrical appliance, TV and Radio draws.

The 120vac to 12vdc power supply for this radio has the Input and Output info but I'm not sure which I use to calculate milliamps or watts.

I know that: E x I = P [watts] BUT WHICH "E" [AC or DC]???

If I calculate 120vAC x 250 mA I get = 30 watts.
If I calculate 13.8vDC x 600mA I get = 8.28 watts

Help?

Vernon
 

jfhtm350

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The rating should be for DC. 13.8 x 0.600 = ~8.28 watts. The scanner is actually using less than 600 miliwatts. Not sure exactly what.

If your using the AC adapter, the kicker is that even though you have the scanner turned off it will still pull power if it is plugged in. All AC adapters are like that. If they are plugged in, they are using power. Unplugging it would take care of that or use a power strip with a switch you can turn on or off. Another thing is the effeciency of the adapter is not 100%. Meaning it is pulling more than what you figure above. So there is no exact number here just a guestamation.
 

mmckenna

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Inefficiencies, as noted above, are variable. Feeling the wall wart being warm will confirm that. The only real way to know accurately and for sure is to use an ammeter to see what the wall transformer is -really- pulling.
 

Circa

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Look on your scanner, on it's label or near where it plugs in.
There should be some info there saying "power" or something like "Input 13.8vDC 600mA", in that example it will draw a max of 600mAh and a voltage of 13.8v.

Watt = Amp x Volt (AMPs not Miliamps, you will need to convert, i.e. 600mA = 0.6amp)

On the wall wart plug itself: 120v would be the INPUT value(The value coming from the wall) on the adapter and the 13.8v would be the output value, the value the wall wart is supplying the scanner.

AC is Alternating Current, which is the value that would come from the wall.
DC is direct current which is what the scanner is using.
There's a downvolting thing in the plug that converts the 120VAC down to the 13.8VDC.

Scannermaster says this: (http://www.scannermaster.com/RadioShack_PRO_652_Police_Scanner_p/22-501869.htm )
Power On the rear of the radio is a center pin coaxial power connector so you can plug in an external power source to run the radio. The external power should be 13.8 VDC, with at least 600 mA. The PRO652 comes with an AC power supply and a DC cable.

Watts = 13.8volts * 0.6amps
So it should be 8.28 Watts max.

If you have a multimeter you could take an actual measurement.
My Pro-651 needs 400mA but it's never required more than 200mA. (I don't charge in the scanner.)
 
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KE5MC

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I have done the following on scanner/radios that I can access the batteries. It easiest if the are AA in spring holders.

Cut an insulator tab the diameter width of the battery and about 1 to 2 inches long. I have copper tape with adhesive on one side, but using two side sticky tape and aluminum foil should work. Put the foil on each side making sure the foil is smaller than the tab and makes no connection to the other side. Leave a small length of foil free from the tab to clip your meter leads to.

Push the battery in a direction that gives you a free area between the battery and contact. Drop the tab in and release the battery. Attach leads to the foil with the meter in current mode. Keep the leads short to minimize voltage drop, which really should not be much for scanners, set meter to higher scale than expected and turn radio on.

Take your reading(s)! Try different operation conditions and volume levels. Interesting to see the current draw as the radio is in different conditions of operation.
 

n5ims

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Because we live Off-Grid [solar power & batteries], I like to know just how much each electrical appliance, TV and Radio draws.

What's important to you isn't what the device draws from its power supply (the ratings for the scanner for example), but what the power supply draws. Many are powered using those horrible wall-warts that draw power even if the device they're supposed to power isn't connected to them. Often they're quite inefficient as well (demonstrated by how warm some can get). It may be that your scanner is rated for 600 mW but that wall wart may draw several watts to provide that small draw the scanner needs.

One suggestion is to get one of those usage meters (e.g. http://www.amazon.com/P3-P4400-Elec...id=1419125554&sr=8-1&keywords=kill+watt+meter) to see what each device normally draws (measure both starting pull and average running draw over a period of normal use). You don't need one for each device, simply measure each in turn and add them up.

Another suggestion (this one's a bit more complex, but can save you loads of wasted power) is to generate and provide both the typical AC for regular devices and DC (generally 12v or so) for devices that use those nasty wall-warts to convert AC to DC. Many devices will work directly on 12v DC and others may need one of those automotive converters to allow them to convert that 12v to what they need (9v DC for example for some handheld scanners). If you do need one of those converters, check to see if it's more efficient to use the DC to DC one or if the AC to DC version is better (and use whichever is most efficient, of course!).
 

majoco

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If you are living "off-grid" I'm quite surprised that you don't already own a multimeter to measure AC and DC currents and the voltages of your batteries, solar cells and power regulators. I would want to have one permanently wired and switched across suitable shunts in case there was an electrical fault which would harm the system. Reasonable quality multimeters are relatively cheap these days, although I would steer clear of the $2 specials. Top of the line Fluke 77/74 series can be bought ex-govt on Fleabay occasionally. Then you can practice the old adage - "When in doubt - test" :)
 

vernongt

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Lot's of good advice and criticism but I've already got my answers from jfhtm350 at the top of this thread.

I have many multimeters of different types, including one that has jaws on it to read current.

All I asked is which piece of information on the radio's power supply do I use to calculate with a CALCULATOR to find current usage.
As for my solar system, it includes lots of measuring equipment with was installed with it. I paid $20,000 for the system and it gives me all that info regarding usage et al.

Amazing how many people; especially those with Ham Callsigns, who wanna give unwanted advice.

jfhtm350 already gave me the answer I asked for!!! Thank you sir.

Thanks all the rest of you as well.
 
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If you need to know how much energy a device consumes you should spend $30 on a nifty device called a Kill A Watt. This plugs into a standard AC wall receptacle and the device you wat to test plugs into it. The screen will display all the info you want, such as Volts, Amps, Watts, plus you can enter how much you pay for electricity and it will display how much it costs to run the device over a period of time. for someone who needs this info it is a handy thing to have around.
 
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