3.5 mm trs jack power carrying points
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- Power
- Mobile Computing
Last response: in Mobile Computing
venky srinivas
May 16, 2014 6:56:07 AM
venky srinivas
May 17, 2014 2:06:06 AM
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Are you dealing with Audio(AC, so the + and - are flipping all the time) or are you dealing with something else(charging maybe?).
I mean current has to flow from tip to speaker(or headphone) to sleeve and ring to speaker(or headphone) to sleeve. If they are powered speakers, the current flow is VERY low and even headphones tend to be under 10-15ma.
Maybe an idea of what you are trying to connect will help.
I mean current has to flow from tip to speaker(or headphone) to sleeve and ring to speaker(or headphone) to sleeve. If they are powered speakers, the current flow is VERY low and even headphones tend to be under 10-15ma.
Maybe an idea of what you are trying to connect will help.
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venky srinivas
May 18, 2014 1:31:01 AM
While some devices will allow power from the USB ports(even with the design intent to be allow power in). This does not work on all devices(many devices have a small part called a diode that only allows the power to flow IN and not out) while USB OTG devices to this by design.
I am not seeing what USB has to do with the 3.5mm jack unless your device charges from it's 3.5mm jack.
If this is the case, It is best to just use a multi meter to find out how the power flows. Some chargers will list it as well.
For instance a Cobra 2-way radio(walkie-talkie) charges from its headset port and uses sleeve as negative and ring as positive. Tip goes unused in this system. So If one wanted to, they could charge it by applying power on the sleeve and ring(that device need 12 volts making USB no good for it without other hardware).
I am not seeing what USB has to do with the 3.5mm jack unless your device charges from it's 3.5mm jack.
If this is the case, It is best to just use a multi meter to find out how the power flows. Some chargers will list it as well.
For instance a Cobra 2-way radio(walkie-talkie) charges from its headset port and uses sleeve as negative and ring as positive. Tip goes unused in this system. So If one wanted to, they could charge it by applying power on the sleeve and ring(that device need 12 volts making USB no good for it without other hardware).
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venky srinivas
May 18, 2014 7:11:35 PM
What exactly are you trying to power off the phone? I do not have that phone to say if it will or will not put out power on its usb connector.
the OTG cable just allows supported devices to use usb hardware like flash drives and keyboards. Having power is to run these devices.
I can not recommend using a phone as a power source when you can get usb power packs for a low price these days.\
I still do not understand exactly what you are tying to do here. You want to power the phone or power something else off the phone?
the OTG cable just allows supported devices to use usb hardware like flash drives and keyboards. Having power is to run these devices.
I can not recommend using a phone as a power source when you can get usb power packs for a low price these days.\
I still do not understand exactly what you are tying to do here. You want to power the phone or power something else off the phone?
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venky srinivas
May 18, 2014 9:48:30 PM
Ok well I have high doubts the 3.5mm jack will do it, but a OTG to USB cable may give you 5 volts to work with. If your phone has the built in diode, you will not get any power out of it.
This is still not always the recommended path to take, but it may work.
The outer pins on usb provide the power. Pin 1 is +5 volts and pin 4 is negative(called ground most of the time). Please remember to select the appropriate size resistor or your LED will burn.
Another small option would be a cheap flashlight that would not require the phone to run.
Image from www.apcc.tk
This is still not always the recommended path to take, but it may work.
The outer pins on usb provide the power. Pin 1 is +5 volts and pin 4 is negative(called ground most of the time). Please remember to select the appropriate size resistor or your LED will burn.
Another small option would be a cheap flashlight that would not require the phone to run.
Image from www.apcc.tk
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venky srinivas
May 19, 2014 9:56:53 AM
You can not tell if it has a built in diode without a meter testing the usb plug. I do not think I have ever tried to take power out of an input on a device like that. I know that some users with battery powered usb changers have had issues of power flowing back into the battery when it dies.
If you are building a flashlight with an LED, you need a resistor to limit the current flowing to the LED, without it the led can burn out rather fast.
If you are building a flashlight with an LED, you need a resistor to limit the current flowing to the LED, without it the led can burn out rather fast.
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venky srinivas
May 19, 2014 6:28:55 PM
k thank u nuke but last question to u if i use 3.5mm slot then it will also require a resistor??? i have searched out about resistors and how to connect but one thing i did not got it that how to select the resistor they are many different sizes can u suggest me for a normal camera flash the resistor ...
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The resistor depends on the current the LED can handle(and the forward voltage of the LED in use. These are not like camera flashes that use much more power.), now you can not just go plug in an led to a 3.5mm jack and expect it to light up. Headphones operate at very low voltage levels. That said you would also have to play a tone to even get it to light.
Some microphones operate with phantom voltage, but chances are this is not going to be how the one on a cell phone works.
You are far better off with something that is just battery operated. If you find you are not getting enough light for image taking, you may be able to build a holder to mount a flash light on the phone(or the phone on the light). to give you faster images(more light means the shutter stays open for less time).
Please note that an actual camera flash is MUCH brighter, but the cell phone sensors are optimized for lower light anyway(and the small size helps with this at a cost to overall image quality).
Edit,
Here is a calculator that allows you to determine the resistor needed.
http://ledcalc.com/
You still need to know info on the power source(voltage) and led(current and forward voltage).
Again, due to inexperience, I recommend against messing with the phone. Get a battery pack for your light instead.
Some microphones operate with phantom voltage, but chances are this is not going to be how the one on a cell phone works.
You are far better off with something that is just battery operated. If you find you are not getting enough light for image taking, you may be able to build a holder to mount a flash light on the phone(or the phone on the light). to give you faster images(more light means the shutter stays open for less time).
Please note that an actual camera flash is MUCH brighter, but the cell phone sensors are optimized for lower light anyway(and the small size helps with this at a cost to overall image quality).
Edit,
Here is a calculator that allows you to determine the resistor needed.
http://ledcalc.com/
You still need to know info on the power source(voltage) and led(current and forward voltage).
Again, due to inexperience, I recommend against messing with the phone. Get a battery pack for your light instead.
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venky srinivas
May 19, 2014 9:54:16 PM
venky srinivas
May 20, 2014 6:46:29 PM
I still do not see HOW you will get the power out of 3.5mm. Unless you can write an app to tell the phone to either listen(you may have a very small bit of current to bias a microphone) or play a VERY loud sound(since audio is technically voltage.).
The input voltage of the battery does not even guarantee the output voltage at any point in the system. Buck converters will lower it as needed and boost converters or charge pumps can increase the voltage beyond what the battery provides.
As an example I have a volt to 24 dc-dc converter(-12 , 0 , +12 technically). Now does this mean running something like a headphone amp off or active combiner of it will produce 24 volts? not likely in fact I would not be surprised if I even needed 0.5-1 volt to make my headphones quite loud. This does not cover the fact that music is AC(diodes are DC).
EDIT. I did some tests for you.
I am going to take the guess work out of it for you.
The lowest forward voltage diode I have will light at about 1.2 volts(it just lights very dim). Now that is VERY loud for audio on many pairs of headphones. The AC nature of audio means you will get a blinking light(and only with the LOUDEST parts of the song) unless you play a sine wave into it(60 hz does work, but I am betting it is not ideal and half the time the led should be out, but it flashes very fast). Adding a full wave rectifier would turn this AC into pulsing DC, but would requite about 0.7 or more volts more due to losses in the rectifier. This is quickly becoming a pain in the but to do with audio
and YES, I just I just set this up to test for you(I used my computer as the sound source since my MP3 player lacks the needed voltage to run it. I also ran everything into an opamp voltage follower to make sure that if I killed anything it would be a 58 cent opamp. It was power from +/-12 volts. I used NO resistor because I did not care if I killed the LED and I know the current from the opamp was going to be low at the required voltage.). This LED has a much lower forward voltage then anything a Cell uses for a flash so you will need MORE voltage to even light it(2-3 volts would be a guess). That is just simply not going to work with most headphone driving devices.
I took this a step further and tried to get power out of a usb device(Creative Zen). No such luck.
Slight light at the end of the tunnel.
If your device uses TRRS(left + right + mic) then you may have mic power. Now how much current this can provide as well as its voltage and if it is on all the time are questions I can not answer.
Would would have to take a meter to see if you have mic power and how much it is.
In my tests, using USB OR audio is just not going to work out well. I did these tests so you do NOT have to. A 4 cell AA or AAA batter holder would give you a nice power source with low resistor values all without potential damage to your phone.
The input voltage of the battery does not even guarantee the output voltage at any point in the system. Buck converters will lower it as needed and boost converters or charge pumps can increase the voltage beyond what the battery provides.
As an example I have a volt to 24 dc-dc converter(-12 , 0 , +12 technically). Now does this mean running something like a headphone amp off or active combiner of it will produce 24 volts? not likely in fact I would not be surprised if I even needed 0.5-1 volt to make my headphones quite loud. This does not cover the fact that music is AC(diodes are DC).
EDIT. I did some tests for you.
I am going to take the guess work out of it for you.
The lowest forward voltage diode I have will light at about 1.2 volts(it just lights very dim). Now that is VERY loud for audio on many pairs of headphones. The AC nature of audio means you will get a blinking light(and only with the LOUDEST parts of the song) unless you play a sine wave into it(60 hz does work, but I am betting it is not ideal and half the time the led should be out, but it flashes very fast). Adding a full wave rectifier would turn this AC into pulsing DC, but would requite about 0.7 or more volts more due to losses in the rectifier. This is quickly becoming a pain in the but to do with audio
and YES, I just I just set this up to test for you(I used my computer as the sound source since my MP3 player lacks the needed voltage to run it. I also ran everything into an opamp voltage follower to make sure that if I killed anything it would be a 58 cent opamp. It was power from +/-12 volts. I used NO resistor because I did not care if I killed the LED and I know the current from the opamp was going to be low at the required voltage.). This LED has a much lower forward voltage then anything a Cell uses for a flash so you will need MORE voltage to even light it(2-3 volts would be a guess). That is just simply not going to work with most headphone driving devices.
I took this a step further and tried to get power out of a usb device(Creative Zen). No such luck.
Slight light at the end of the tunnel.
If your device uses TRRS(left + right + mic) then you may have mic power. Now how much current this can provide as well as its voltage and if it is on all the time are questions I can not answer.
Would would have to take a meter to see if you have mic power and how much it is.
In my tests, using USB OR audio is just not going to work out well. I did these tests so you do NOT have to. A 4 cell AA or AAA batter holder would give you a nice power source with low resistor values all without potential damage to your phone.
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venky srinivas
May 21, 2014 1:02:58 AM
venky srinivas
May 21, 2014 1:05:22 AM
I do not use Facebook to be honest. Do not even have a login for it.
But I did get some of the testing out of the way for you
For finding just the right resistor if you happen to have a viable resistor(if you want to start very safe 10k will only let 1miliamp into a 2.7 forward led. This is a very safe start.) you can start out dim and slowly brighten the light to the level you get when the flash was on a phone. At that point you can measure the resistance and voltage drop to get all the info you need for that LED.
But I did get some of the testing out of the way for you
For finding just the right resistor if you happen to have a viable resistor(if you want to start very safe 10k will only let 1miliamp into a 2.7 forward led. This is a very safe start.) you can start out dim and slowly brighten the light to the level you get when the flash was on a phone. At that point you can measure the resistance and voltage drop to get all the info you need for that LED.
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venky srinivas
May 21, 2014 9:52:56 AM
venky srinivas
May 21, 2014 9:56:36 AM
On most phones it would be the right right next to the sleeve. Again, you you pull too much power(mic's do not tend to need much power) you may damage something.
Using a meter and a TRRS to TRRS cable you can find out for sure. Sleeve is almost always ground so you would just meter for DC under 12 volts to find the location of power.
I am on the other side of the world in Canada.
If you can get your led working on 5 volts from USB, you can always connect it to an external usb charger instead of the phone.
5 volts on a 3 volt drop would need something in the 120 - 150 ohm resistor. to get into the 15-20ma range. Lower value resistors will allow more power, but if you exceed the led power rating it will burn(sometimes it even changes color before it fails.).
Using a meter and a TRRS to TRRS cable you can find out for sure. Sleeve is almost always ground so you would just meter for DC under 12 volts to find the location of power.
I am on the other side of the world in Canada.
If you can get your led working on 5 volts from USB, you can always connect it to an external usb charger instead of the phone.
5 volts on a 3 volt drop would need something in the 120 - 150 ohm resistor. to get into the 15-20ma range. Lower value resistors will allow more power, but if you exceed the led power rating it will burn(sometimes it even changes color before it fails.).
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venky srinivas
May 21, 2014 6:46:57 PM
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Before wiring anything, you need to see if the OTG cable even gives you power. If it does not, all this work is for nothing.
Even a cheap meter will help you better understand what is going on.
USB cables have power on the outer edges on the normal PC style plug that most of these OTG cables become. The issue here is if the device has to negotiate before allowing power or not. I do not use OTG so have never looked into it.
To get your self started maybe you should take power from a normal usb port(very carefully, do not use the data pins, just keep then from touching anything and tape them off separately).
Take the Black wire and connect it to the LED's cathode end(on a normal led it has a shorter pin and is the longer side inside the led, but you may not be able to see that on this setup). Connect the resistor(for 5 volts lets use 120-200 ohms or so to limit yourself to 15-20ma current flow) to the other lead on the LED(anode) and the other end of the resistor to the red wire. With a meter you can be 100% sure what you are connecting by pre checking the power.
If all is good this will allow a computer usb port to light your led.
Please note starting with a large resistor(I have a 5k 1 turn variable that allows better control to find just how much light I would want. It was picked up for something else, but works for this as well) and working down is a good way to fine tune the brightness.
I can not offer you a simple yes or no answer on how to connect to your device because I do not own the device and they do not make the specs available to the general public. The mic wire may have 5 volts or only 1.5. I have no way to tell and again current limits are another issue.
This is a writeup that has some info on how the OTG setup works. You will quickly see that without being designed for it, chances are it will not work for your application.
http://www.ti.com/lit/wp/sszy001/sszy001.pdf
Even a cheap meter will help you better understand what is going on.
USB cables have power on the outer edges on the normal PC style plug that most of these OTG cables become. The issue here is if the device has to negotiate before allowing power or not. I do not use OTG so have never looked into it.
To get your self started maybe you should take power from a normal usb port(very carefully, do not use the data pins, just keep then from touching anything and tape them off separately).
Take the Black wire and connect it to the LED's cathode end(on a normal led it has a shorter pin and is the longer side inside the led, but you may not be able to see that on this setup). Connect the resistor(for 5 volts lets use 120-200 ohms or so to limit yourself to 15-20ma current flow) to the other lead on the LED(anode) and the other end of the resistor to the red wire. With a meter you can be 100% sure what you are connecting by pre checking the power.
If all is good this will allow a computer usb port to light your led.
Please note starting with a large resistor(I have a 5k 1 turn variable that allows better control to find just how much light I would want. It was picked up for something else, but works for this as well) and working down is a good way to fine tune the brightness.
I can not offer you a simple yes or no answer on how to connect to your device because I do not own the device and they do not make the specs available to the general public. The mic wire may have 5 volts or only 1.5. I have no way to tell and again current limits are another issue.
This is a writeup that has some info on how the OTG setup works. You will quickly see that without being designed for it, chances are it will not work for your application.
http://www.ti.com/lit/wp/sszy001/sszy001.pdf
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venky srinivas
May 28, 2014 7:02:02 AM
venky srinivas
May 28, 2014 10:50:19 AM
Best solution
Honestly my the way that Li-ion chargers work, I do not think you will ever get power out of the usb port unless it was designed for it(on the go or similar has been designed from the ground up to not only give you power, but make sure it is 5 volts.).
I have looked quite deep into getting power out of such devices and it simply does not work. Looking at MANY different usb chargers they are all built to prevent any power from moving in the reverse direction. This protects the IC's(these ic's can do many things and are not that easy to identify from a tear down video) dealing with the charging as well as the device providing the power.
I have looked quite deep into getting power out of such devices and it simply does not work. Looking at MANY different usb chargers they are all built to prevent any power from moving in the reverse direction. This protects the IC's(these ic's can do many things and are not that easy to identify from a tear down video) dealing with the charging as well as the device providing the power.
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venky srinivas
May 28, 2014 10:18:56 PM
nukemaster said:
Honestly my the way that Li-ion chargers work, I do not think you will ever get power out of the usb port unless it was designed for it(on the go or similar has been designed from the ground up to not only give you power, but make sure it is 5 volts.).I have looked quite deep into getting power out of such devices and it simply does not work. Looking at MANY different usb chargers they are all built to prevent any power from moving in the reverse direction. This protects the IC's(these ic's can do many things and are not that easy to identify from a tear down video) dealing with the charging as well as the device providing the power.
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venky srinivas
May 28, 2014 10:19:57 PM
Again, due to the charging system used on modern electronics they will all have some way to prevent power from flowing backwards.
Even on to go phones / devices will need to negotiate before switching on the ability to send out power.
I highly recommend you build a battery back OR use an battery powered usb charger. This will always give you 5 volts making it easy to use with almost any LED.
I am sorry this did not work out, but power from the headphone jack was going to be difficult and do get any useful voltage you would need to make it play a sine wave, rectify that sine wave and then boost that voltage to something usable. This all requires parts. While not overly costly, it would be not recommended for a first project.
Even on to go phones / devices will need to negotiate before switching on the ability to send out power.
I highly recommend you build a battery back OR use an battery powered usb charger. This will always give you 5 volts making it easy to use with almost any LED.
I am sorry this did not work out, but power from the headphone jack was going to be difficult and do get any useful voltage you would need to make it play a sine wave, rectify that sine wave and then boost that voltage to something usable. This all requires parts. While not overly costly, it would be not recommended for a first project.
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venky srinivas
May 29, 2014 11:22:28 AM
venky srinivas
May 29, 2014 11:23:46 AM
A sine wave a steady ramp upto a positive and down to a negative(in this case). It is a AC wave that has more voltage and a nice high peak. This is why it can work under the right circumstances. and LED will only make use of the rising part of it.
You can download a tone generated sine wave off the internet or even get on on youtube.
To get the most power of it t, you would need a rectifier. this will cost you voltage. In order to get the higher voltage you want, you need some kind of boost converter or charge pump.
This is way outside the scope of a first time builder.
If you playback a sine wave on your phone and measure the output from the headphone jack, you will see how many volts RMS the device can produce. If this number is too far under the forward voltage of an LED, it will not even light(resistor or no resistor).
I do not quite see what you are trying to do aside of extract power from the phone to run a flash. This is a job that can much more easily be done with 4 aaa batteries(could use less, but 5 gives you a nice 6 volts to work with.) and a single resistor.
You can download a tone generated sine wave off the internet or even get on on youtube.
To get the most power of it t, you would need a rectifier. this will cost you voltage. In order to get the higher voltage you want, you need some kind of boost converter or charge pump.
This is way outside the scope of a first time builder.
If you playback a sine wave on your phone and measure the output from the headphone jack, you will see how many volts RMS the device can produce. If this number is too far under the forward voltage of an LED, it will not even light(resistor or no resistor).
I do not quite see what you are trying to do aside of extract power from the phone to run a flash. This is a job that can much more easily be done with 4 aaa batteries(could use less, but 5 gives you a nice 6 volts to work with.) and a single resistor.
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