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Potentiometer 1kOm as voltage divider 0 to 5V. how?

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edvardas

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Hello,

I gave a potentiometer 1kOm, so it goes from 0 to 1 kOhms. I want to use this potentiometer as speed sensor for my application. The problem is that i want to use it with velleman K8055 board. At first i thought that i just lead 5V though the potentiometer, but there is way too less resistance.

Could any1 help me to do this?

principle is like this:

https://imageshack.us/photo/my-images/853/26506950.jpg/

potentiometer will be moved by my application. Currently 0 to 1kOhm resistor makes absolutely no difference at all, it moves by 2 bards of 255..

I think i need a voltage divider circuit or something
 
hi,
Your image shows the potentiometer is connected incorrectly.

Connect the two ends of the pot to +5V and 0V, [ so its across the 5v supply to 0v] use the wiper pin of the pot as you signal input to the ADC.
 
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thanks, it really works... I'm so embarassed to this 'newbie' question. I've just used multimeter to test it, and the resistance between 1 and 3 pins was constant, and between 2 and 3 it varied, o i've used those pins..

It works pefrect with 7805 voltage regulator as power supply, but if i connect K8055 output, the output voltage instantly drops to 1.83V,. even if the potentiometer is set to 0, so i get only readings from 0 to 1.8V. i wonder why?
 
thanks, it really works... I'm so embarassed to this 'newbie' question. I've just used multimeter to test it, and the resistance between 1 and 3 pins was constant, and between 2 and 3 it varied, o i've used those pins..

It works pefrect with 7805 voltage regulator as power supply, but if i connect K8055 output, the output voltage instantly drops to 1.83V,. even if the potentiometer is set to 0, so i get only readings from 0 to 1.8V. i wonder why?

hi,
As you know the K8055 gets its +5V/0v from the USB cable to the PC.

You must be shorting out the USB +5v,, with a 1K pot the current thru the 1K is only 5mA, the regular USB connector can supply upto 100mA.

Does the K8055 work OK, from the USB 5V when the pot is NOT connected.???

Have you connected the 7805 and the USB +5V together!!!!

Can you post another diagram showing how you have connected the pot.??
 
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hi,
As you know the K8055 gets its +5V/0v from the USB cable to the PC.

You must be shorting out the USB +5v,, with a 1K pot the current thru the 1K is only 5mA, the regular USB connector can supply upto 100mA.

Does the K8055 work OK, from the USB 5V when the pot is NOT connected.???

Have you connected the 7805 and the USB +5V together!!!!

Can you post another diagram showing how you have connected the pot.??

K8055 works fine without connected to pot. When i set DAC1 to max i have 4.6V to the output, but once i connect the pot the output i get 1.8V. I've connected like this:

https://imageshack.us/photo/my-images/197/67666026.png/

but if i use 7805 voltage regulator i connect it similar, just instead of dac1 i connect to the output terminal of 7805, it works fine then

I don't short anything, and everything seems to be working fine
 
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hi,
The DAC output is via a 1k5, so adding a 1K to 0V will pull down the output voltage.

EDIT:
If you set the 100K trim pot on the A1 to max [100k] and use a 100K pot instead of a 1K pot, you should get close to 5V on the DAC1 output.
 
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Thank you for the info :) i know there is a way of using PIC18 with this board, but just can't find good guide on how to do this. K8055 is great, just a bit slow
 
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and what exactly have changed? How did u programmed new PIC18?

hi,
The hardware changes are shown on the circuit diagram in post #8, I used Oshonsoft to write the new program for the 18F2550 in the K8055 PCB.
 
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