boylesg
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I got it working with a totem pole comprised of 2SC4793 and 2SA1837 - the light bulb lights up dimly.A safety resistor is needed, otherwise there is nothing to stop severe spikes from going through the led's.
For the fun of it, I'm running a simulation.
If you put the NPN on top and PNP on the bottom, then no resistor or diode is needed to limit bias. Nevertheless it's a good idea to include the resistor, for safety.
Larger capacitors will lengthen the current spikes, as well as slow down the action so your eyes can follow the led flashes.
It wont work with capacitors.
Link D1, D2, R3 they aren't needed, connect 555 pin 3 directly to the 2 bases of the transistors.
Connect the 2 emitters directly to the LEDs, no series resistor.
Replace the caps of 680nF with 2 resistors of 1K.
If you want more light reduce the value of 1K resistors.
If you want to light up small bulbs connect one side of each bulb to the emitters and the other side of one bulb to ground, the other side of the other bulb goes to +12V. If you wish I can send you circuit.
It can be done without the transistors because the 555 gives enough current to drive LEDs or 1W bulbs.
Are you saying that you wanted to keep us busy until your bits arrive?! very thoughtful.
If you make the base resistor zero ohms (no diodes either) and place your lamps across the transistors you will get the bright lights you desire...
This is what I've already advised boylesg. Please read his embarrassing response that followed, post #7.
The datasheet for the 555 shows that its output has an old fashioned TTL darlington transistor emitter-follower to pull up its output to about 1.0V to 2.5V less than its supply voltage. The datasheet for the modern TC4422 Mosfet driver IC shows that its output has Mosfets that switch very close to the supply and to ground.One thing that stumps me is how they manage to get very close to Vcc output from those gate drive ICs. With the darlingtons I get Vcc minus around 2V on the output.
How do you get this sort of circuit to work?
View attachment 116746
I don't understand what I am doing wrong.
A complementary pair like this works perfectly well as part of a class AB amplifier but there seems to be no way to make it work from 555.
It appears that the 555 cannot switch the BCs on enough for them to generate or sink enough current from their emitters.
I have had this sort of problem before with a Jacob's Ladder kit, from Jaycar, that simply did not work once soldered. It also was driving a single BC327 which in turn drove a automotive power darlington.
- - - Updated - - -
It works just as well without the diodes, but I can only get it to output enough current to drive a LED directly, both to GND and from Vcc.
But what I don't understand is why it seems impossible to get enough current out of the totem pole to light up an automotive light bulb....even dimly.
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