Help needed with rocket timer circuit

[Hal8472]

Hi. I am trying to figure out how to assemble a circuit. Not a lot of components but it's solution has eluded me for some time. It's creator has long since moved on to other things. While only a few components it gets into some complexities with resistor-capacitor charging initiated by a switch opening. This part is beyond my simple knowledge. I know there are other timers out there but I kinda have my heart stuck on this one, partly because I have been trying unsuccessfully for a while.

Here's a link to the circuit
http://www.rocketreviews.com/scratch-12-ounce-timer-by-jonny-dyer.html

I have uploaded the schematic from the site and the description. I have also uploaded how I wired it up and my notes. My notes has the parts I used and what I think the pins are for the transistors. This could be my problem.

Parts
3v battery, 2xAAA holder
SC1 is IRF530n
1k resistor
22k resistor (instead of potentiometer )
220uF capacitor
2x PNP Transistor. A1015

So I have it wired up, remove the connection wire shorting the capacitor and nothing happens. Not sure where to start troubleshooting. Help would be great.
Thanks
Andrew

 

[AnalogKid]

Perhaps a word or 50 about what the circuit is supposed to do might help figure out if it is doing it. Simple stuff like -
Is the circuit in the rocket or on the ground?
What is the desired timing range?
What is the "load"?
Does the timer need to be adjustable?

ak

 

[Colin Mitchell]

The transistors are ECB

 

[Hal8472]

Sorry, good point.

This timer is intended to fire an ejection charge in a rocket when it reaches the highest point in its trajectory. The load is an electronic match with various amounts of black powder. This charge pops off the nose cone and deploys the parachute. With rockets this delay would be anywhere between 10 and 30 seconds. The initiation switch could detect the launch in a variety of ways. The easiest is just having the switch which is a wire tied with string to the launcher. As the rocket fires the connecting wire stays behind. Also, some rockets fire a second larger parachute as the rocket gets closer to the ground, up to a minute.

The timer itself is ideally not adjustable on the completed unit. Setting up each one could be adjusted by changing the resistor or capacitor. But I would build one to match the rocket and motor combination and not change it on the field.

Thanks

 

[Hal8472]

The transistors are ECB

Do I have them backwards or totally out of whack?

 

[Bluejets]

Yes
As Colin says, Emitter = 1 , Collector = 2, and Base = 3

Do I have them backwards or totally out of whack?

 

[Bluejets]

Also I notice you have a mosfet in place of the SCR.
I find things easier when circuits are drawn in a conventional manner and have sketched it out below.

 

[AnalogKid]

It sounds like he says printed circuit boards are more trouble than they're worth, then offers to sell you one.

For "any good PNP transistor" there are at least two different pin assignments. Without the part numbers and datasheets for the transistors and SCR you are using, there are no answers.

ak

 

[Bluejets]

Transistors were quoted as A1015
SCR's are mostly the same but it was quoted as 200v 6A

Hal, ...BTW....SC1 is IRF530n ...is a mosfet

That website link threw up a virus warning also...??

 

[Hal8472]

I really appreciate this help. Thanks for the comments and redrawing the schematic, it is clearer.
My PNPs are A1015s and I have labelled them EBC and rewired them.
Oops, MOSFIT bad, changed to SCR BT169D. BT169d looks to me like pin out CGA.
Now the buzzer is on from when connected. No delay. Any ideas on the next step?

 

[Hal8472]

It sounds like he says printed circuit boards are more trouble than they're worth, then offers to sell you one.
ak

Tried that, but he has totally gone. No answer to email, and gave it half a year in case he was very busy

 

[Bluejets]

Might have blown the transistors by being connected wrong.

 

[Hal8472]

Might have blown the transistors by being connected wrong.

Yup. It's good to have lots. Replaced and now it's totally silent.
I checked the delay, 22k ohms & 220 uF gives a delay of 5s. Well past that now.
If transistors broken and it makes sound, when fixes gives no sound, what's missing?is something wrong with transister wiring?

 

[Hal8472]

I have been looking at other timer circuits for similar functions. It looks, like other circuits use one PNP & one NPN Transistor. Does that make more sense?

 

[AnalogKid]

There are many different ways to combine a couple of transistors to do this task. Two NPN, two PNP, one of each, small MOSFETs - all work approximately the same way. It depends more on what you have than any "right" way. Usually I try to minimize the number of different components, so I would start with two identical transistors of whatever I have.

OTOH, one NPN and one PNP can be combined into a discrete pseudo-SCR, possibly eliminating the actual SCR in the circuit depending on the load current. I've seen e-matches from 1 to 36 ohms. What is the range of values for your application? And, do the burn through to an open circuit?

ak

 

[Bluejets]

Is your buzzer actually a buzzer and not just a piezo unit requiring an external oscillator driver to operate?
Perhaps it would be a good idea to just use an LED as an indicator and a resistor of appropriate size to suit what ever voltage you are running.

 

[Hal8472]

Still not doing anything. Tried the change to LEDs but no change. Analogkid mentions there are lots of ways to do this but it's funny that we can't get one to work. I am beginning to think something key was missing from the circuit. It's only a few parts though...
Anyone else have an idea if I have wired it wrong or if the circuit needs to be changed?

 

[Colin Mitchell]

1. Does that little round black thing beep when connected to the battery?
2. Does that little round black thing beep when you connect the C and A leads together?
3. Does that little round black thing beep when you remove the first transistor?

 

[Hal8472]

The little round black thing is a buzzer.
1. Yes
2. Yes
3. No. What does that mean?

Thanks

 

[Colin Mitchell]

Remove the second transistor and put the 1k in place of the C and E leads.
4. Does that little round black thing beep?