# increasing voltage or current

#### Gryd3

Jun 25, 2014
4,098
what happens if the LED's doesn't have same Current consume for example if first is 15 second is 20 and third is 25? will it be like the voltage in parallel i mean they wont work ?
so i have to control the current,did we do that in parallel?why we have to do that now?
and can i give every string 12 v since they are serie?
and since the 2 strings are going to be parallel does they have to have same Voltage consume?
Well... when I mentioned using a resistor on each LED, we did control current
You *can* connect a 15mA, 20mA, and 25mA LED all in series. You need to make a decision here though. The current through a series string like this *must* be the same through all components... It's a *law* not a guide-line. So if you size your resistor to allow 25mA through, you can damage the first, and possibly the second.
If you size the resistor to allow only 15mA through, then all 3 LEDs will run at, or under their limit. The 20mA and 25mA will not be as bright *as they could be*, but will still light. You can understand that if you have too much variation, bad things, or no things can happen xD ... ie, a 15mA LED and a 300mA LED . You either immediately kill the little one, or the big one hardly does anything.
As far as the strings are concerned, *you* dictate what voltage they will run at with the resistor you choose.
If you base your calculations on a 12V supply that will allow the resistor to provide 20mA to the LEDs, the increasing the voltage will increase the current as well.
If you have designed each string to run on 12V with the appropriate resistors and number of LEDs, then you can connect each string in parallel and by a happy camper

*notes:
When you connect something in parallel, the voltage on *each* parallel piece will be the same.
So... You had initially (incorrectly) wired the LEDs directly in parallel... this resulted in the same Voltage being applied to them all and the lower rated LEDs would get damaged.

When you connect something in series, the current through *each* piece will be the same.
So... when you connect 3 LEDs and a resistor in series, you should properly size the resistor to allow 20mA (example) to flow through... this also means that 20mA is going through each LED in the same string.

You *can* and often will have a mix of series and parallel components... much like what you are building now.
You will end up having multiple groups in parallel, each group is a string of LEDs and a resistor that is in series.
Each string will be provided with the same voltage from one end to the other. (The voltage may not, and does not need to be the same part-way through all the strings! They can vary as long as the *total* voltage for the string is 12V) All of the components in a single string will have the same current flowing through them. *BUT* you could easily have one string made with 30mA LEDs, and another string made with 10mA LEDs.... because they are separate strings you don't have to worry about forcing 30mA through the poor little LEDs

#### kourosh daryaee

May 12, 2016
38
Thank you Gryd3 that was all good news !!!

#### BobK

Jan 5, 2010
7,682
The other thing to know is that you will not see much difference between 20mA and 25mA through the same LED.

Bob

#### kourosh daryaee

May 12, 2016
38
The other thing to know is that you will not see much difference between 20mA and 25mA through the same LED.

Bob

Another good news !!!

#### kourosh daryaee

May 12, 2016
38
This is the final result
Thank you . it is a great experience to get help from such a great community .

http://sendvid.com/ko6gsz4w

#### Gryd3

Jun 25, 2014
4,098
This is the final result
Thank you . it is a great experience to get help from such a great community .

http://sendvid.com/ko6gsz4w
So glad you got it working well!
I was a little concerned when you first came in and set you soldered and glued it all together already

Thank you for sharing the results.!

#### kourosh daryaee

May 12, 2016
38
A new problem , very new and unrelated !!!
i have 4 input wire in this device , 2 for supply and 2 for audio input.
when i connect this thing and my speaker which works on 12volt too ,to the battery and audio input to the speaker ,speaker works well but the light device starts panicking ,and when i connect the minus wire to the battery it completely stops working(when audio wire is connected to the speaker ,but no problem when its connected to an other audio input.).
now i suspected it might be the 2 minus wire of supply and signal board that i connected to emitter in this circuit :

Am i right? see if you can help me with this problem.
Thanks.

#### Gryd3

Jun 25, 2014
4,098
A new problem , very new and unrelated !!!
i have 4 input wire in this device , 2 for supply and 2 for audio input.
when i connect this thing and my speaker which works on 12volt too ,to the battery and audio input to the speaker ,speaker works well but the light device starts panicking ,and when i connect the minus wire to the battery it completely stops working(when audio wire is connected to the speaker ,but no problem when its connected to an other audio input.).
now i suspected it might be the 2 minus wire of supply and signal board that i connected to emitter in this circuit :

Am i right? see if you can help me with this problem.
Thanks.
Here is where things might get tricky...
For that transistor to work, you need to have a 'common' point. (Which is usually ground).
That way, there is a circuit for the audio signal into R1, into Q1, and down to ground which is connected back to the audio output negative.
The second circuit is the + of another supply, through the motor or lights, through Q1, and down to ground which is ALSO connected to the - of the other supply.

These two circuits MUST overlap for this to work... The potential problem is if there is an accidental circuit from the + of the other supply through the motor, through Q1, *but* back through R1, then the audio circuit could be damaged!

This is not a problem if you use a seperate batteries, or *isolated* power supplie to power the audio device and the add-on gear. Otherwise, you need to test if the audio device has made either one of it's 'Audio outputs' *common* to either one of the power inputs.

The panicky behaviour is caused by a lack of a proper 'circuit', so the transistor find itself biased at awkward times.

#### kourosh daryaee

May 12, 2016
38
Here is where things might get tricky...
For that transistor to work, you need to have a 'common' point. (Which is usually ground).
That way, there is a circuit for the audio signal into R1, into Q1, and down to ground which is connected back to the audio output negative.
The second circuit is the + of another supply, through the motor or lights, through Q1, and down to ground which is ALSO connected to the - of the other supply.

These two circuits MUST overlap for this to work... The potential problem is if there is an accidental circuit from the + of the other supply through the motor, through Q1, *but* back through R1, then the audio circuit could be damaged!

This is not a problem if you use a seperate batteries, or *isolated* power supplie to power the audio device and the add-on gear. Otherwise, you need to test if the audio device has made either one of it's 'Audio outputs' *common* to either one of the power inputs.

The panicky behaviour is caused by a lack of a proper 'circuit', so the transistor find itself biased at awkward times.

But when i use supply for both speaker and light ,and connect audio(its the audio jack not the supply of audio board ) to some other device other than speaker things works well. panic happens when i try to connect supply and audio jack to the speaker which has a audio output.

#### Gryd3

Jun 25, 2014
4,098
But when i use supply for both speaker and light ,and connect audio to some other device other than speaker things works well. panic happens when i try to connect supply and audio to the speaker which has a audio output.
Can you sketch me a picture?
It still sounds like one of the two circuits is either not complete, or there is an accidental circuit.

May 12, 2016
38

#### kourosh daryaee

May 12, 2016
38
since - of the signal board(which connected to audio jack) and - of supply is connected to emitter and speaker i suspected that it might the problem.

#### Gryd3

Jun 25, 2014
4,098
I'm willing to bet that the 'speaker' has one of it's audio outputs connected to one of it's supply inputs.
Could also be the actual output signal being unfit for use.
You can try to put a capacitor in-line with the positive signal line. Called a 'decoupling' capacitor, it's meant to prevent current flow through the signal line. You can also use a 'ground loop isolator' which will break the electrical connection completely for the signal wire making it impossible for an accidental loop to form between the supply and signal lines.

#### kourosh daryaee

May 12, 2016
38
I'm willing to bet that the 'speaker' has one of it's audio outputs connected to one of it's supply inputs.
Could also be the actual output signal being unfit for use.
You can try to put a capacitor in-line with the positive signal line. Called a 'decoupling' capacitor, it's meant to prevent current flow through the signal line. You can also use a 'ground loop isolator' which will break the electrical connection completely for the signal wire making it impossible for an accidental loop to form between the supply and signal lines.

Thanks, i try to check whats inside the speaker (which i am not sure i can do anything special about it there.).

#### Gryd3

Jun 25, 2014
4,098
Thanks, i try to check whats inside the speaker (which i am not sure i can do anything special about it there.).
Unplug it all, and measure between the supply inputs and the speaker outputs... look for very low, or 0Ω resistance, and tell us what wires this happens to be between.

A redesign of the circuit with a PNP transistor may be required...
I think the 'safest' bet is the ground loop isolator, or perhaps the decoupling capacitors

#### kourosh daryaee

May 12, 2016
38
Unplug it all, and measure between the supply inputs and the speaker outputs... look for very low, or 0Ω resistance, and tell us what wires this happens to be between.

A redesign of the circuit with a PNP transistor may be required...
I think the 'safest' bet is the ground loop isolator, or perhaps the decoupling capacitors

there is a 100k-200k Ω resistance everywhere between supply in and speaker out.

#### Gryd3

Jun 25, 2014
4,098
there is a 100k-200k Ω resistance everywhere between supply in and speaker out.
Hrm..
To be honest, I'd love to give you the exact cause and solution to this, but I can only recommend what I would try... and that would be decoupling caps, or the ground loop isolator.
Does @BobK mind looking at post #51 to offer his suggestion on why the device may be acting up?

#### kourosh daryaee

May 12, 2016
38
Thank you again.
I don't know about ground loop isolator but decoupling caps is some kind of redesign from what i remember, it change's the switch circuit ,so if you can tell me how to do the ground loop isolator that would be great(if it's easier than decoupling caps and it's calculations).

#### kourosh daryaee

May 12, 2016
38
Hrm..
To be honest, I'd love to give you the exact cause and solution to this, but I can only recommend what I would try... and that would be decoupling caps, or the ground loop isolator.
Does @BobK mind looking at post #51 to offer his suggestion on why the device may be acting up?

Ground loop isolator Works very well ...
Thank you.

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