PIC - Outputting variable voltages - Page 2 - Electronic Circuits Projects Diagrams Free

superflux · 10th October 2009, 09:11 PM

Just looking for a couple set voltages around 4.3 and 4.7 volts for this project. However; I'm also looking for a design that would allow me to use this same design in other projects for dimming leds where PWM is not possible.

binzer · 10th October 2009, 10:59 PM

Quote:

Originally Posted by superflux

To my knowledge, this is a emitter follower scenario. The more voltage placed into the transistor, the higher the resulting voltage out the emitter - no?

Depending on the switch position, either PORTB 6 or 7 will be turned on via software, suppling 5 volts, to the selected port, dropped down slightly by the resistor/diode combo into the transistor.

I am all ears and willing to learn.

Thanks!

Well your schematic shows the emitter is GROUNDED, thus output will always be zero.
It's obvious to me that there should be a resistor on the emitter and your output pulled from across it, just drawn wrong.
Mike.

be80be · 11th October 2009, 01:25 AM

I used a 12f508 with resistor ladder by setting any combination of the four pins high
I could go from 0 to 5 volts makes a real good led controller

superflux · 11th October 2009, 01:27 AM

Quote:

Originally Posted by be80be

I used a 12f508 with resistor ladder by setting any combination of the four pins high
I could go from 0 to 5 volts makes a real good led controller

It definitely sounds like the way to go.

be80be · 11th October 2009, 01:42 AM

Quote:

Originally Posted by superflux

It definitely sounds like the way to go.

I got the idea from here My PIC Projects
read down to the sine wave I did it for the voltage not a sine wave. so i'm just setting the port to get what voltage I need.

You get 16 possible resistor combination's

ronsimpson · 11th October 2009, 02:50 AM

superflux,
You did not understand my last post about driving a LED. You do not have one output =1 and the other =0!
The pins have three states. 1, 0, Z (z=input)
pin1, pin2, current
0, 0, 10mA
Z, 0, 8mA
0, Z, 2mA
Z, Z, 0mA

superflux · 11th October 2009, 03:28 AM

Quote:

Originally Posted by ronsimpson

superflux,
You did not understand my last post about driving a LED. You do not have one output =1 and the other =0!
The pins have three states. 1, 0, Z (z=input)
pin1, pin2, current
0, 0, 10mA
Z, 0, 8mA
0, Z, 2mA
Z, Z, 0mA

On the contrary, I did understand and I thought it was a good solution.

I was simply asking if the when 2 or more PORTs are set to OUTPUT and are connected and one of them is "1" and the other is "0", does that "0" represent 'ground' and if so, can I assume that it will ground out the voltage sent from the other connected PORT that is set to "1" (high)?

I guess what I'm asking is when an OUTPUT port is set to "0" is that GROUND or just 0 volts?

blueroomelectronics · 11th October 2009, 05:09 AM

PWM is a much better way to drive an LED, why wouldn't you want to use it?

ronsimpson · 11th October 2009, 05:51 AM

0=0 volts, 1=supply voltage, assuming the current is low. Z= any voltage from 0 to supply and no current.

superflux · 11th October 2009, 11:42 AM

Quote:

Originally Posted by blueroomelectronics

PWM is a much better way to drive an LED, why wouldn't you want to use it?

During the ADC process, where I sample with a delay between each of the 8x sample reading, I would get a bright blip out of the LED.

I use PWM for many other projects, but I since I need that longer sample time, I don't want to run into issues with it.

Is the R2R ladder not a good solution in your opinion?

be80be · 11th October 2009, 12:07 PM

Quote:

Originally Posted by superflux

During the ADC process, where I sample with a delay between each of the 8x sample reading, I would get a bright blip out of the LED.

I use PWM for many other projects, but I since I need that longer sample time, I don't want to run into issues with it.

Is the R2R ladder not a good solution in your opinion?

You can go from 0 to 5 and full on at any voltage.

You have no duty to worry about.

I've done some things with leds and R2R make the leds look like there on fire
I couldn't get it to work with pwm

blueroomelectronics · 11th October 2009, 04:41 PM

That blip can be fixed with software.

be80be · 11th October 2009, 06:45 PM

All blip can be fixed with software. Some time down the road if you don't run out of time lol

superflux · 11th October 2009, 11:05 PM

I can probably program the LED PWM in the ADC delay, but if the R2R ladder works just as well, then why bother with the extensive programming?

be80be · 11th October 2009, 11:15 PM

Quote:

Originally Posted by superflux

I can probably program the LED PWM in the ADC delay, but if the R2R ladder works just as well, then why bother with the extensive programming?

That's what I think keep it simple R2R 10 lines PWM a page and 2 week making it do what you want.

What's in your code LOL

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10th October 2009, 09:11 PM	#16
superflux	Just looking for a couple set voltages around 4.3 and 4.7 volts for this project. However; I'm also looking for a design that would allow me to use this same design in other projects for dimming leds where PWM is not possible.

11th October 2009, 01:25 AM	#18
be80be	I used a 12f508 with resistor ladder by setting any combination of the four pins high I could go from 0 to 5 volts makes a real good led controller __________________ Burt http://mybe80be.com http://stores.shop.ebay.com/mybe80be__W0QQ_armrsZ1

11th October 2009, 02:50 AM	#21
ronsimpson	superflux, You did not understand my last post about driving a LED. You do not have one output =1 and the other =0! The pins have three states. 1, 0, Z (z=input) pin1, pin2, current 0, 0, 10mA Z, 0, 8mA 0, Z, 2mA Z, Z, 0mA

11th October 2009, 05:09 AM	#23
blueroomelectronics	PWM is a much better way to drive an LED, why wouldn't you want to use it? __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/

11th October 2009, 05:51 AM	#24
ronsimpson	0=0 volts, 1=supply voltage, assuming the current is low. Z= any voltage from 0 to supply and no current.

11th October 2009, 04:41 PM	#27
blueroomelectronics	That blip can be fixed with software. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/

11th October 2009, 06:45 PM	#28
be80be	All blip can be fixed with software. Some time down the road if you don't run out of time lol __________________ Burt http://mybe80be.com http://stores.shop.ebay.com/mybe80be__W0QQ_armrsZ1

11th October 2009, 11:05 PM	#29
superflux	I can probably program the LED PWM in the ADC delay, but if the R2R ladder works just as well, then why bother with the extensive programming?