Man...I understand what your saying...it won't be a changing balance...other than when you press the pedal to go to a different balance.

I COULD have done that with my cry-baby but it's not what I'm going for.

 

Then you need two dual pots and a TPDT switch.

__________________
Uncle $crooge

 

Yep I know i need two Dual Pots...but why a Triple Pole? 1 Pole for Audio and 1 Pole for the power to the LED's and IC signal input (ie: goes through the resistor to the signal input).

 

The first pole switches the audio between the two pots.
The second pole applies power to the LED that indicates which pot is selected.
The third pole switches between the sliders of the pots to the LM3914.

The third pole cannot light the indicator LED. It is a variable voltage that is too low to light an LED.

__________________
Uncle $crooge

 

Right ok so I can't have it with my method of having the 3.3333V for Rhi or maybe 9.9999? And then feeding 9V to the Pot in parallel with the indicator LED.

Your saying that I should hook it up so the Pot is getting 1.25V from pin 7 (I think) and using that across the potentiometer with the wiper going to a switch?

(I'm sorry about asking a bunch of probably annoying questions I'm just trying to understand this all fully)

 

You can make the pin 7 any voltage from 1.25V and up. But the circuit works well and is the easiest with it at 1.25V.
You don't want to mess up pin 7 with additional current from the indicator LED.

__________________
Uncle $crooge

 

Ok that makes more sense now. I assume TPDT pots are common?

Also let me just run this by again:
-1.25V to one side of the Pot
-1/9th the Pots resistance Resistor followed preceded by switch to Wiper and Signal In.
-Small resistor to the other side of Pot to ensure first light is on?

 

Ok so this is how you recommended to setup the IC correct?


Also since all those resistors are in parallel with the 560ohm won't I have to adjust it's value so that the total resistance among all those resistors are 560ohm?

Attached Images

Balance Dot Audioguru.JPG (51.1 KB, 7 views)

 

1) You don't need the 330 ohm resistor in series with the LEDs because the LM3914 regulates the current in the LEDs.
A resistor is needed if the IC is in the bar mode and many LEDs are lighted then their total current is high which would cause the IC to get too hot.
2) Every electronic circuit should have a supply bypass capacitor.
3) The resistors and the 10k resistance of pin 6 are in parallel with the 560 ohm resistor creating a total resistance of 510 ohms. Then the LED current is 12.5/510= 25mA.

I think I calculated the resistors so that the 1st LED lights when the selected pot is at minimum and the 9th LED lights when the pot is at max. Then the middle LED will light when a pot is in the middle.

Attached Images

Balance_Dot_Audioguru.PNG (54.9 KB, 6 views)

__________________
Uncle $crooge

 

I was just wondering why every circuit needs a supply bypass capacitor. Also how would I go about calculating the needed value. (I'm thinking it has something to do with the current or voltage.) Does this also mean I will need one for the Indicator circuit? Or will this act for both?

Also could I not have just adjusted the 560ohm resistor so that the current was still 22ma. I'm not going to but I'm just wondering.

Thanks again.

 

Some circuits oscillate without one.
A battery has an internal resistance that increases as it runs down. Then the supply voltage changes as the load current changes. A supply bypass capacitor smooths the voltage changes so they don't change sharply and the change is much less. The capacitor powers the circuit when the battery can't.

If you have only one battery then your circuit needs only one supply bypass capacitor. If it has RF then a ceramic disc capacitor must also be used since it works well at RF frequencies and an electrolytic capacitor works well at low frequencies.
A very low current low frequency circuit needs 0.1uF to 10uF.
A "medium" current low frequency circuit needs 100uF to 1000uf.
A high current low frequency circuit needs a high capacitance.

If the 560 is changed to 620 ohms then the LED current in the circuit with the pots is 22mA. The max current for most LEDs is 30mA to 40mA. You won't notice any difference between an LED at 22mA and another at 25mA. Double the current is only a little brighter because your vision's response to brightness is logarithmic (before your iris appies its automatic brightness control).

__________________
Uncle $crooge

 

Ok so it's basically guess work on the capacitor then? or an educated guess that roughly 1/4 W is 100uF.

 

10uF would probably work fine in your circuit. If it had audio as well then 100uF or 1000uF would be needed to keep the audio from being affected by the LEDs turning on and off.

__________________
Uncle $crooge

 

Ok well this is what I have for final. If all looks good I'll draw up a PCB and get a prototype going.


Thanks a lot for your help thus far Audio.

Attached Images

Balance Dot5.JPG (115.2 KB, 5 views)

 

It looks fine.
Let us know how well it works.

__________________
Uncle $crooge