Ive never seen this, but I Made a USB charging cable for my Pro-97 PICS!!!

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StatuSChecKa

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Hey fellas, I was reading on the newest Radio shack scanner last week, and I saw that is charges VIA Mini-USB. I was Jealous.
So I was pondering a way for me to scan when at work, without lugging around a ac adapter everywhere, and so I dont have to drain my battery every friggin day.

*Note, if you try this, please try on an old scanner first, as I am not responsible for you or your scanner getting shocked* The reason I did this on my 97, is that I had a few beers, and am ready to order a brand new scanner IF I need to!
.
What you need is the raw end of an adapter wire that fits the scanner:


And old USB cord that you'll cut to shreds.

Strip the end of the USB, and Get the Red and Black wire striped back a quarter inch. Important: you will combine the Green and White wires, so the computer will give the port some power. (Very low voltage, but powers the scanner :) ).



Strip the Ad adapter end, and connect the negative to black, and the positive to red.

Make it look neat, and your done! Make it as long or short as you want.
 

StatuSChecKa

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Another great part is that I can power/charge my scanner, WHILE it is hooked up to the LINE IN jack on my computer, WITH NO humming sound or interference. (For when I record)
Cant do that with an AC Adapter....

It's been about 10 minutes plugged in so far, and It has not blown up. It seems to bet putting out 7-8 V, because the contrast is not as strong as it is when 9V is plugged in.
 

j0nnyb1aze

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Yup, simple concept. Red and black are +/- 5v and green and white are data.

Keep in mind though USB2.0 is spec'd only to provide 500mA per port. (900mA in 3.0).

So make sure your scanner can run on 5v and doesn't draw more than 500mA.
 

StatuSChecKa

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Bro I have no Idea what your talking about.
I may buy a cheap Multi Meter to check it out. I unplugged it for now, cause I have no use for it tonight. But I do assure you that It was nice and bright and working properly.
 

j0nnyb1aze

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How do you charge a 6 volt radio with a 5 volt USB port?
Well, USB actually is 5v +/-0.25v so it can supply up to 5.25 volts, I wouldn't be surprised to see a 6v radio power up on 5.25 volts(it certainly won't charge the battery to 6v). I'm more concerned about current draw.

Atmittedly I don't know the power requirements of the pro-97(my bc250d is 500ma) so you may well be w/in this. Just make sure you're supplying appropriate power to your radio if you do this.
 

datainmotion

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Congratulations on the effort!

Have you given any thought on how to prevent current flow from the batteries back into the computer your "charger" is hooked to?
 
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datainmotion

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Keep in mind though USB2.0 is spec'd only to provide 500mA per port. (900mA in 3.0).
Spec'd is the key word here...

From Charging Batteries Using USB Power - Maxim:

"USB ports do NOT limit current. Though the USB spec provides details about how much current a USB port must supply, there are mile-wide limits on how much it might supply. Though the upper limit specifies that the current never exceed 5A, but a wise designer should not rely on that. In any case, a USB port can never be counted on to limit its output current to 500mA, or any amount near that. In fact, output current from a port often exceeds several Amps since multi-port systems (like PCs) frequently have only one protection device for all ports in the system. The protection device is set above the TOTAL power rating of all the ports. So a four-port system may supply over 2A from one port if the other ports are not loaded. Furthermore, while some PCs use 10-20% accurate IC-based protection, other will use much less accurate poly-fuses (fuses that reset themselves) that will not trip until the load is 100% or more above the rating."
 

mancow

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Powering it is one thing but charging is another. I guess it would make for a handy alternative to a wall wart if you were just wanting to power it for a while.




Well, USB actually is 5v +/-0.25v so it can supply up to 5.25 volts, I wouldn't be surprised to see a 6v radio power up on 5.25 volts(it certainly won't charge the battery to 6v). I'm more concerned about current draw.

Atmittedly I don't know the power requirements of the pro-97(my bc250d is 500ma) so you may well be w/in this. Just make sure you're supplying appropriate power to your radio if you do this.
 

j0nnyb1aze

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Spec'd is the key word here...

From Charging Batteries Using USB Power - Maxim:

"USB ports do NOT limit current. Though the USB spec provides details about how much current a USB port must supply, there are mile-wide limits on how much it might supply. Though the upper limit specifies that the current never exceed 5A, but a wise designer should not rely on that. In any case, a USB port can never be counted on to limit its output current to 500mA, or any amount near that. In fact, output current from a port often exceeds several Amps since multi-port systems (like PCs) frequently have only one protection device for all ports in the system. The protection device is set above the TOTAL power rating of all the ports. So a four-port system may supply over 2A from one port if the other ports are not loaded. Furthermore, while some PCs use 10-20% accurate IC-based protection, other will use much less accurate poly-fuses (fuses that reset themselves) that will not trip until the load is 100% or more above the rating."
interesting read.
 

DonS

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You may be able to power the scanner from a 5V USB port, but it's unlikely that you'll charge the batteries very well, given that the charge termination voltage should be about 1.8V per cell. Without going through the charts and the math, I'd guess that you'll never charge 4 NiMH cells above 25% of capacity if you're only giving them the USB port's maximum of 5.25V.
 

StatuSChecKa

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Thanks for yall's technical breakdown. Like I said, i dont see me using this to really charge the batts, I have a AC adapter that is stationary for that.
If I do have it hooked up to a computer, I will probably take the batteries out as to not have any current bleed back INTO the computer.
As long as My scanner is safe while it is connected to the computer with or without the batteries. I call it a Job well done, because I can listen at work without battery drain, and I can record without a hum or interference.
--Jeff
 

djeplett

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FWIW I have powered my 97 for years with a wall wart that was labeled for 300mA. I never charged batteries in it, but it ran for years just receive only on that wart. So my guess is the cable you made should work awesome for receive only. I wouldn't trust the PC's power supply for charging the batts as you'd hate to damage the motherboard just trying to do that. But in your case, receiving only should work great. Nice job thinkin' with yer noggin'.
 

gmclam

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PRO-97 headphone jack has no ground

Another great part is that I can power/charge my scanner, WHILE it is hooked up to the LINE IN jack on my computer, WITH NO humming sound or interference. (For when I record)
Cant do that with an AC Adapter....
The "problem" is that the headphone jack of a PRO-97 (or any of the GRE made scanners I own) have a ground on them. Each side of the signal connects through a resistor. I was able to get rid of the hum by attaching a separate wire from the radio's ground to the computer's ground, even when powered from an AC adapter.
 

StatuSChecKa

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Ya I figured it was a grounding issue of sorts. I was about to purchase a heavier duty Male to Male plug with thicker wire, I guess that wouldn't of help either.
 

13riverking

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You may be able to power the scanner from a 5V USB port, but it's unlikely that you'll charge the batteries very well, given that the charge termination voltage should be about 1.8V per cell. Without going through the charts and the math, I'd guess that you'll never charge 4 NiMH cells above 25% of capacity if you're only giving them the USB port's maximum of 5.25V.
just wondering where the data for the termination voltage for 1.2v NiMH cells came from?
 
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pro92b

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Looking at application notes and datasheets from Duracell, Energizer, Panasonic, and Sanyo it appears that the fully charged voltage for a NiMH cell is about 1.55V. This is at room temperature and a 1C charge rate. The voltage varies a fair amount at other charge rates and temperatures.

The PRO-97 needs about 7 volts to charge batteries at about 2/3 its normal charge rate. At 5.5 volts the battery is not charging at all. The radio does operate at 5 volts but the voltage regulator that powers the audio amp needs about 6 volts to be in regulation. Lower voltages mean less audio output, more distortion etc. There is a protection diode in the radio that keeps the battery from trying to push current to the power jack. The diode also causes voltage drop when powering the radio from an external source. A 5V input to the power jack results in about 4.3V available to the radio circuits.
 
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