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generate square wave

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digitalp

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Hi
pls see the attachment.
Why the leds donot light up when switch S1 is closed?
and not be able to generate square wave?
any specific settings needed for op-amp?
any mistake in connections?

Thanks.
 

Attachments

  • design1.png
    design1.png
    179 KB · Views: 343
The load is excessive and will drag the output down. If you are expecting, for argument's sake, 9V output pulses and each LED has a rated forward voltage of 2V, then the expected load would be 6 x (9-2)/100 Amps, =420mA. The poor old opamp is rated for a maximum output current of only 40mA (with a 15V supply)! Hint: when designing a circuit always check the datasheets of the components you plan to include.
BTW, you shouldn't post the same question in two forums.
 
Ok, sry.
I am provided with LM358N op-amp. What settings in terms of V, A I have to set for simulation?
I really need guidance.
 
Why didn't the LEDs lit up?
I am reaally confused. Anything wrong with the circuit? pls....
 

Attachments

  • LM358N_Datasheet.pdf
    1,006.3 KB · Views: 392
Did you read the data sheet?
Hint: look for the Electrical Characteristic, Output current, Source.


Did you read Alec's posting?
 
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The value you seek is given at a supply voltage of 5V, 15V and 30V. Interpolate at 9V.
 
still unsure value for input voltage for an op-amp?
Forget that, for now. Concentrate on selecting an output load which is within the capabilities of the opamp.
 
Disconnect the LEDs, and rerun the sim. The oscillator cannot oscillate with the switches open.
 
Hi,

The data sheet has a clear example of the square wave oscillator on page 14. Use that schematic.

As others have pointed out, you also need to remove the LEDs and resistors. You'll need a driver transistor (later) to drive that many LEDs.

If you use the schematic on page 14 you'll get this working right away. Then you can add a driver later.
 
Write down what you are trying to accomplish.

It could be as simple as ...

Have six, 30 mA white LEDs flash once per second using a 9V battery to run for 10 hours.

From there you can decide on what you need to be done.

FYI - yes, I know that task is not a good example because of the battery.
 
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Ok,thanks.

My objective of this circuit : visibility of road signs such as "slow ", "work in progress", is being affected by poor weather or lighting conditions.
Using this circuit visibility of these signs is increased by contrasting the blinking speed of bright LEDs. This attracts attention of drivers.

1)How can I improve this circuit by providing solutions to practical problems other than i have mentioned earlier?

I am provided with components such as:
solar panel,mosfet, BJT, trimmer, hall sensor , 2-input NAND, 2-input NOR ,speaker, resistors, capacitors, temperature sensor,toggle switches,push buttons, op-amp, LDR.

2)How can I incorporate some of these components into the circuit.

Any advice?
Thanks.
 
1)How can I improve this circuit by providing solutions to practical problems other than i have mentioned earlier?

Your goal is to improve the visibility of various warning signs. We have some around here that remind people to "Do not stop on the tracks" at a railroad crossing. From my observation, the sign is encircled with bright white LEDs, a lot of them. They flash 24-7. You will need high intensity during the daylight hours and lower intensity at night to not blind the drivers.

So, let's look at your project:

1. Solar panel to charge the battery pack. What voltage and current can I expect on a cloudy day?
2. The battery ... some voltage at some ampere-hour rate. What is the ampere-hour rate of my electronics and lighting?
3. A number of LEDs encircling the sign ... about 1 per 2 inches. So a 24 inch x 18 inch sign would probably be around 20 LEDs. How much current will the LEDs draw at bright intensity?
4. The electronics:
- battery charge monitor
- dusk/dawn detector
- dual PWM ... to control the intensity
- LED driver capable of handling 1.5 x the maximum current of the 20 LEDs
- heat sinks if needed

These are a quick list of some things to consider.

If you are just doing this for a homework exercise, it can be considerable smaller project.

Are you restricted to just the list of components you provided?
 
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