556 Blinking Light Project help

[vne147]

In your first test you had a 10 ohm resistor to the led so you would have burnt the led out with excess current through it

Agreed.

There are tons on 555 calculators on the web. Here's one:

555 Astable Circuit Calculator

The duty cycle is what you need to pay attention to for varying on time vs off time. A duty cycle of 50% for example has an on time and off time that are equal. A duty cycle of 25% has an off time 3 times the on time.

You can use the calculator to provide some guidance and like SABorn said you can just fiddle around with different components and values until you get the look you want.

Good luck!

 

[Mouse51180]

That is a nice web calculator...

I am confused a little though. The tutorial I followed has a resistor between the Vcc pin and Discharge pin...but the calculator doesnt show that...Is that because I am using a 556 chip or was that something someone just added for more protection from buring something out?

I have also seen some tutorials that use a transistor in the project as well...?!?

 

[fernandoagv]

i have this problem watching a non-polarized capacitor

 

[vne147]

That is a nice web calculator...

I am confused a little though. The tutorial I followed has a resistor between the Vcc pin and Discharge pin...but the calculator doesnt show that...Is that because I am using a 556 chip or was that something someone just added for more protection from buring something out?

I have also seen some tutorials that use a transistor in the project as well...?!?

The calculator does have a resistor between Vcc and the discharge pin. It is shown as R1 between 9V (Vcc) and pin 7 (discharge). As far as the transistor, it's hard for me to comment on the purpose without seeing the specific circuit you are referring to but one common use for a transistor in a 555 circuit would be to switch the output.

The 555 can only supply so much current through the output pin. I think around 200 mA. In your project, the output is only turning on an LED which does not exceed the current the 555's output can supply. However, if it was being used in a circuit where something needed to be turned on requiring more current than the 555 could supply (like a motor for example) then the output could be connected to a transistor. The 555 output would switch on or off the transistor (which only requires a small current) and that transistor would in turn supply the higher current to the load.

I don't know if that's the case in the tutorial you're referring to, it's just one scenario where a transistor could be used in conjunction with a 555.

i have this problem watching a non-polarized capacitor

Stop watching it...problem solved.

 

[Reloadron]

Just as a footnote to online 555 calculators a really good one that can be downloaded and used anytime on you computer can be found here. Plus for any questions about it, you need not go far.

Ron

 

[KJ6EAD]

Some breadboard survival tips:
Solderless breadboards don't like having component leads or wires inserted that exceed 20 AWG and work best with 22 AWG wires. You can replace the damaged contact strips from underneath if you have some spares from a damaged board of the same type. To mount TO-220 packages in a breadboard, use a pair of pliers to twist each of the leads 90° before inserting.