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circuit help

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Hello,
The lights are visible But very dimly. i am attaching the picture when it is in analog mode.see the light intersity of last 9 LEDs and the other(upper) ones.
actually the voltage from the output pin of the microcontroller for the 9 LEDs is only 0.67 voltages.But it should be 5v. i don't know why it is happening. this is why the 9 LEDs are dimmed. But i believe that with 0.67v the Base-emitter junction is forward biased so the LEDs should light in their normal way. why are they dim?
or it may also be happening that when the voltage is so low from the microcontroller then current may also be Low. that may be the reason why the LEDs are dim. what do you sujjest?
 

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can i use the two stages of transistor to take the Ic around 100mA? in first stage Ib will go from 1mA to 10mA and at the collector of te second stage the Ib will become 100mA. will it work?
 
The output of a microcontroller into a low current load is a high of near +5V and a low of 0V. Yours is only +0.67V when it is read on a slow meter because it is pulsing at a high frequency (you can't see it pulsing and your slow meter cannot read properly) at a low duty-cycle which causes the LEDs to be dimmed.
Look at the output with an oscilloscope to see the pulsing and see the low duty-cycle.
It is the program that is causing the pulsing.
 
ok. Did you see the last picture i posted? and right away i replaced the transistor 2N4401(i was using this one) with BC337, and the intensity of the LEDs increased a bit. can i decrease the value of base resistor to increase the base current so increase the collector current.?
 
2Nxxxx transistors have the opposite pins to BCxxx transistors. Look on their datasheets for the pins.
A transistor has very low current gain when its E and C pins are connected backwards.

Use Ohm's Law to determine that the 330 ohm base resistor supplies plenty of base current for the transistor to turn on. If the output of the microcontroller goes to +5V and the base-emitter voltage of the transistor is 0.7V then the resistor (and the base of the transistor) have a current of (5V - 0.7V)/330 ohms= 13mA.

Blue LEDs are about 3.3V. Then the 100 ohm current-limiting resistor in series with each one has a current of (5V - 3.3V)/100 ohms= 17mA. The total LED current is 153mA and with a base current of 13mA the transistor turns on completely.

Your dimming is because your power supply voltage sags or because the output from the microcontroller is pulsing.
 
Hello Audioguru.
today i've changed the whole board of LEDs thinking that the LEDs be creating the problem. now each and every LED is new and working fine. But as i connected the circuit the 9 LEDs are continuously ON. i don't know why? the output from the Microcontroller is same (+0.67v). And the LEDs are lighting bright enough But are continuously ON.
Can you suggest to check something.
Thanks
 
The output from the microcontroller should be +4.5V to +5V when high which turns on the transistor properly so the LEDs are bright.
The output from the microcontroller should be 0V when low to completely turn off the transistor and the LEDs.

With the base of the transistor in series with the 330 ohm base resistor that is connected to the output of the microcontroller, connect the base to ground and the LEDs should completely turn off. It they do not turn off then the transistor is wired wrong. If they do turn off then the program for the microcontroller is wrong.

EDIT: Are you making this circuit on a breadboard with very long connecting wires? Then the wires act like antennas and a nearby radio station or high voltage electricity wires are picked up and lights the LEDs dimly.
 
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Building a propeller clock looks like fun. I have access to some 10,000 rpm compaq server hard drives and would like to use them for my propeller motor. Trouble is I don't know how to trick the motor into running for me. Anybody care to help me with some information.
Also, correct if I'm wrong, hard drives are magnetic storage devices, but the disks, when taken out of the hard drive, are not attracted to a magnet and drill chip from drilling holes aren't magnetic either. My son tells me that they can't be erased with a magnet either. Anybody know the explanations for this or what the disks are made of?
Thanks,
Kinarfi
 
@ kinarfi
you are right that the hard disks are magnetic storage devices. and the a magnet can erase all the things inside the hard disk, when a magnet is brought near to the hard disk. i did my hard disk clean once or twice using magnet.
and for propeller clock you do not require that much RPM. take a simple 12v DC motor and that would do your work as mine working for me. look up the pictures i posted. they all are of my propeller clock. start yours, it's not so hard to design one.

@Audioguru
i am building my project on vearoboard. i soldered every component. and today i desoldered the transistor and connected the output pin of the microcontroller to the 9 LEDs Cathodes (they are as they were in configuration as you told me) and i did not remove the 100 ohm resistor. with doing this the 9 LEDs are working very fine. But when i am connecting the transistor as as you told me, then all the 9 LEDs are going ON all the time. i tried changing the transistor But the 9 LEDs are continuously ON.
 
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ejector;934678today i desoldered the transistor and connected the output pin of the microcontroller to the 9 LEDs anodes (they are as they were in configuration as you told me) and i did not remove the 100 ohm resistor. with doing this the 9 LEDs are working very fine. But when i am connecting the transistor as as you told me said:
Didn't you know that the NPN transistor inverts the logic? Without the transistor, the LEDs light dimly when the output of the microcontroller goes low. With the transistor, the LEDs light brightly when the output of the microcontroller goes high.

To have the same logic as before, you could drive the anodes of the LEDs from a PNP transistor then the cathodes of the LEDs are connected to ground. Then the LEDs will light brightly when the output of the microcontroller goes low.
 
Sorry! i was talking about the Cathodes. i meant to say that i connected the cathodes of the 9 LEDS and then connected this node to the Collector of the transistor.
Now, when connecting the cathodes of the LEDs directly from the output of the Microcontroller the 9 LEDs are working fine But when connecting through the Transistor the 9 LEDs are Continuously ON. though these 9 LEDs have to be ON only in Analog mode to make Hands of the clock, But these 9 LEDs are continuously ON from the time, i am supply power to the circuit.
 
You did not understand a word I said that the NPN transistor inverts the logic which causes the LEDs to be on all the time.
Using a PNP transistor to drive the anodes of the LEDs will fix it.
 
ok. today i gonna do this But one last is remaining in my clock that what about the remote? who to fix it's Frequency? i've downloaded it's Report. which says that tune the 500k ohm resistor in the clock's main circuit and in the remote till the clock start working. now it is very irritating. and i've to tune the resistor every second. isn't there a way to fix it.? please check it circuit, that is on the first page of this forum.

thanks
 
Building a propeller clock looks like fun. I have access to some 10,000 rpm compaq server hard drives and would like to use them for my propeller motor. Trouble is I don't know how to trick the motor into running for me. Anybody care to help me with some information.
Also, correct if I'm wrong, hard drives are magnetic storage devices, but the disks, when taken out of the hard drive, are not attracted to a magnet and drill chip from drilling holes aren't magnetic either. My son tells me that they can't be erased with a magnet either. Anybody know the explanations for this or what the disks are made of?
Thanks,
Kinarfi

Got to thinking about the 10,000 rpm propeller clock, at that speed, I'd probably be picking LEDs out of the walls. I'd still like to know how to power up a hard drive motor, if any knows how. I appears to be 3 phase, at least it has 3 leads.
 
@ kinarfi
NOT 3 But it must has 4 pins.
usually a hard drive has 4 power pins. two for +5v and ground and other two are for +12v and ground.
And make sure no one should be near ,when you run your motor at 10,000 RPM :)
 
what about the remote? who to fix it's Frequency? i've downloaded it's Report. which says that tune the 500k ohm resistor in the clock's main circuit and in the remote till the clock start working. now it is very irritating. and i've to tune the resistor every second. isn't there a way to fix it.?
The datasheet for the Chinese RX-2B remote decoder IC says it is made for cheap toy cars so of course it is not accurate enough for this project.

The project seems to be designed a long time ago by somebody who knows nothing about electronics. Post a link to the project.
 
**broken link removed**
this is the link of the site from where i downloaded the project But now the site is closed i think. it is not opening.
you try to open the link. if it doesn't open then tell me, i downloaded every thing on this project that was available on the site.
 
at the moment i am not at home and all the decuments of my project is at home. so i'll be able to post them as soon as possible.
 
at the moment i am not at home and all the decuments of my project is at home. so i'll be able to post them as soon as possible.

connect o/p of micro controller through 1k resistor to base of transistor.also on the collector side increase the series resistor from 100ohm to 220ohm.I think, this happens because even a very small base current can drive transistor into saturation unless base resistor is connected.
 
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