# HELP! LED "level meter" circuit using Integrated circuit.

Discussion in 'The Projects Forum' started by deadlyzxcv, Jul 8, 2015.

Jul 8, 2015
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Hi.

I am doing a project using 555 IC and potentiometer/variable resistor, creating pulse to control a propeller spinning speed.

I wanted to add in a 6 LED, 3 Green/2 Yellow/1 Red, which will be control by the same potentiometer/variable resistor that able to indicate the spinning speed of the propeller.

Example: in green and yellow zone, the spinning speed is safe. But when it reaches red zone, it will mean that is spinning too fast and need to slow down.

This is my idea:
but instead of using the Arduino card, i need use other components, ICs, etc.

The attached file I had uploaded is the circuit that controls the spinning speed of the propeller. So, I need to combine the circuit diagram in the photo and also the LED circuit together into one circuit diagram.

Hope you guys can share some tips and ideas, Thank You.

2. ### djsfantasi AAC Fanatic!

Apr 11, 2010
2,902
877
Have you heard of the LM3914? Google for a datasheet. It is an LED Bar Graph Driver.

3. ### AnalogKid Distinguished Member

Aug 1, 2013
4,687
1,297
By calculation, in your circuit the 555 frequency varies between 54.25 Hz and 55.29 Hz. That's not much, less than 2% difference. What are the fastest and slowest propeller speeds you want? Also, how is the 555 circuit driving the motor?

ak

Jul 8, 2015
6
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Thanks for the tip. I will look it up.

Jul 8, 2015
6
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For this project, I have to create and design a circuit to make the propeller to spin by using variable resistor to control the speed which will affect how high is it flying. And we will then solder the circuit onto circuitboard and connect it to the device.

So, we are using the 555 timer IC to generate pulse. With the variable resistor, I am able to change the pulse width produced by the 555 which will affect the spinning speed of the propeller.

I does not know about the speed that the propeller is spinning.

6. ### AnalogKid Distinguished Member

Aug 1, 2013
4,687
1,297
The "basic control circuit" you posted is ok as a concept drawing, but it will not do what you want with the components shown. There will be very little speed change across the adjustment range. Also, the 62K base resistor is too high if the output transistor is driving the motor directly.

ak