Hi there - I think I've got my head around a basic circuit, but I want to create something a bit more tricky - a single blinking LED. I would like to achieve this using NPN transistors, capacitors, 1 led and resistors.

Has any one seen any good schematic or diagram with how the current, voltage make it work?

I've been trying to work it out on paper to no avail.

Thank you!

 

See if you can scare up a 2N2646 UJT and make the circuit at the link - http://www.circuitstoday.com/ujt-relaxation-oscillator

Place your LED in series with the resistor R.

 

You could look into a 2 transistor multivibrator. That circuit is simple, straightforward, and will blink 2 LEDs alternately.

Schematic, 1 of thousands

 

I guess another follow up question would be - is it normal to try to do this in this manner - or should i be using something like a 555 chip? I've seen them mentioned a lot with regards to oscillation.

 

I guess another follow up question would be - is it normal to try to do this in this manner - or should i be using something like a 555 chip? I've seen them mentioned a lot with regards to oscillation.

A 555 timer is the best option for stability and accuracy, but of course requires the 555 chip itself, which isn't among the components you specified.

 

I would use clock chip. We did this sort of thing in second year EE course, but we used frequency generator for the clock.

That is also the point of the multivibrator mentioned above, based on values of the components, it will act as frequency generator, the clock.

Connect the clock and source to AND gate. Source is always On, when clock is On, the AND gate output is On and led light up. Otherwise, led does not light up.

So all you need is clock chip, AND gate IC like 74LS08, led, resistor, voltage source.

 

I guess another follow up question would be - is it normal to try to do this in this manner - or should i be using something like a 555 chip? I've seen them mentioned a lot with regards to oscillation.

There are a lot of ways to do it, all of them need an oscillator of some sort.

Flashers, Chasers, 555's Blog by member Bill Mardsen here has great information and schematics.

 

I like the low voltage long duration variety myself.

This is simple.

The 555 Projects

CMOS 555 Long Duration Minimum Parts LED Flasher

I figure it will last a year with two alkaline D cells. This circuit depends on the low power supply voltage, do not use more voltage or things will smoke. You can buy the CMOS 555 from Radio Shack.

The low power supply voltage makes the chip into the LED resistor. More power supply voltage and that chips resistance goes down.

 

Considering you component requirements there's nothing wrong with this circuit, just replace one of the LEDs with a dummy resistor or increase the value on one side to simulate a similar load.

http://www.reprise.com/host/circuits/transistor_flasher.asp