That's easy - a 556 has two 555's inside it. Just duplicate the circuit. The 7812 is a 12V voltage regulator and the 1N4001 and 220 uF cap on the left are the power supply circuit. Everythiing else is the circuitry you need to wrap around a single half of the 556. So you just double up the parts count, check the pinout for the 556 and make adjustments for the differing pinout and you're ready to rock. Looks like an evening with some breadboard and a little pile of parts.

Warren

Oh man, Scott, what kind of trouble are you getting yourself into now???

I just got back from a trip to the home brew store, at least MY creation is going to be drinkable - at leas I hope.....

Scott, what Warren said. Simple. Just remember you have a 200 mA limit to what you can sink or source.

Scott, what Warren said. Simple. Just remember you have a 200 mA limit to what you can sink or source.

What??? 😯 Whats sink and sorce?? 😕

You guys got to remember, it took me 3 days to get this working on a test board. With the schematic right in front of me! 😕

Looks like an evening with some breadboard and a little pile of parts.

Warren

Yes maybe for you. 😕
To answer Gregs question: "propane powered machine guns".
They dont fire projectiles of coarse. But they do make a loud rapid repeating report.
And yes it works when you get the gas flow, and the spark timing just right. I had one working once. Till the lady across the street threatened to call the athorities!
But the whole idea is to have two guns firing oposite of each other and maintaining sincronized fire. Will a 556 chip do that?? I guess my question is inside the 556, do the two 555s keep time with each other?

They are two, independent timers on one chip. You just adjust them to any sequence you want. Forget the sinking and sourcing. If you've made a 555 work, then you're fine. Do you have a 556 schematic? You can get one online. Just keep searching.

Looks like an evening with some breadboard and a little pile of parts.

Warren

Yes maybe for you. 😕
To answer Gregs question: "propane powered machine guns".
They dont fire projectiles of coarse. But they do make a loud rapid repeating report.
And yes it works when you get the gas flow, and the spark timing just right. I had one working once. Till the lady across the street threatened to call the athorities!
But the whole idea is to have two guns firing oposite of each other and maintaining sincronized fire. Will a 556 chip do that?? I guess my question is inside the 556, do the two 555s keep time with each other?

You need to be in the Mad Scientists club in Denver. That's the kind of stuff they do. Like the 200yd caulking tube cannon....

They are two, independent timers on one chip. You just adjust them to any sequence you want. Forget the sinking and sourcing. If you've made a 555 work, then you're fine. Do you have a 556 schematic? You can get one online. Just keep searching.

I have the back of the 556 package. Can you make one time the other?
I have seen schematics online.

I was looking for a way for them to keep time with each other but firing opposite of each other.
To give the sense of a more rappid fire.

If you want them synchronized, that's different. You'd have to tweak the timing pots to get equivalent timing as what I was talking about was two independent circuits with a common power supply.

Why not use a single 555 with a flip-flop circuit on the output so that alternating pulses fire different output transistors?

As far as sinking or sourcing current, it's all dependent on the output transistors and the voltage regulator capability.

Warren

Again, what Warren said. Yes, you can use one to trigger the other when they're in one-shot mode. Let me go through old schematics that I have... somewhere... Warren's right about the flip-flop chip, too. The timing is done with pots (variable resistors).

Again, what Warren said. Yes, you can use one to trigger the other when they're in one-shot mode. Let me go through old schematics that I have... somewhere... Warren's right about the flip-flop chip, too. The timing is done with pots (variable resistors).

These contraptions already have variable resistors on them.
I have two built that work. They use propane cut off silenoids from fork lifts to controle the propane and oxygen. Two for each gun (4 in all)
You can adjust each gun separatly. When you push the firing button
the power opens the silenoids and starts the plug firing all at once.
If every thing is adjusted right ( the gas flow and the spark timing)
they start firing. But they dont do it in time with each other.
The original pair of Spandous on a DR1 (Fokker Triplane) were not timed together either. But with a firing rate of 8 to 9 rounds a second per gun in the originals, the propane guns cant keep up (only about half)
So........if I can get the two guns to fire oposite of each other in time, it with give the sense of a faster firing rate.
At any rate this flip flop circuit sounds interesting.

Heres a picture of a pair of Spandous with a plane attached to them.
The one below I think is a 3/4 scale tripe.

Scott, sorry it's taken so long to get back to you. I found a schematic that I can modify that will probably do what you need. I'll have to draw it up. But I have too many things to do this week, plus my wife's birthday, another job interview Thursday, and getting rockets ready for NCR's Pawnee Open. I know you understand. In the meantime, find a schematic online that will time the 555's sequentially. Remember to reverse bias your relays (solenoids) with diodes so you don't fry your chip.

Scott, sorry it's taken so long to get back to you. I found a schematic that I can modify that will probably do what you need. I'll have to draw it up. But I have too many things to do this week, plus my wife's birthday, another job interview Thursday, and getting rockets ready for NCR's Pawnee Open. I know you understand. In the meantime, find a schematic online that will time the 555's sequentially. Remember to reverse bias your relays (solenoids) with diodes so you don't fry your chip.

Bruce some of that is Greek to me. No rush anyway. Just in the pursuit to finish projects Ive started in the last 5 years and havent completed.
(They are already half paid for) Its a cheaper way to keep me busy and clean up the the garage at the same time. 😉

Is the DR1 the plane you are building? I think you told me once but forgot... The old WWI planes are the only reason I would get my pilots license. They are so elegant and amazing.....
Now this propane gun totally makes sense.

On a side note, do you have the plans for the guns? It would be fun to make some dummy versions of them.