Transistor Timer

[Nitrophuric Aci]

I have become befuddled by a simple schematic thttp://www.putfile.com/pic.php?img=3218501hat teases my brain. I built a time delay circuit for anything from a digital alarm clock to a countdown timer. Now when tested on breadboard with a flashlight bulb in lieu of an ignnitor or detonator, the circuit worked perfectly. Now when I actualy used a 1.5 volt from an alarm clock timer to the circuit it doesnt work. Any ideas, because this simple setup could work with any kind of detonation via remote i mean it is applicable to just about anything. Why cant I get it to work now?

[BlackFalcoN]

Replace the NPN transistor by a SCR PNPN thyristor. Collector-Base-Emitter becomes Gate-Anode-Cathode.

Also, as a safety feature, it would be wise to implement a LED (with a resistor) parallel over the detonator to indicate the circuit's status, as well as a switch to reset the SCR thyristor.

[Electronitro]

With such considerable efficiency to obtain a simple NPN transistor at any radio shack as opposed to an SCR or any type of thyristor, therein lies the ultimate question of how such an operation can be accomplished. I for one attempted the utilization of a MOSFET in lieu of the standard transistor in hopes that the gate, source, and drain would act appropriately for the operation perhaps subsequently copying the anode, cathode and gate as found in the SCR Much to my dismay, it also did not work properly.
USE
The typical NPN transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. The transistor is the fundamental building block of the circuitry and because of its fast response and accuracy, the transistor is used in a wide variety of digital and analog functions, including amplification, switching, voltage regulation, signal modulation, and oscillators.
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That being a fact, one can only assume that NitrophuricAci has the right idea to quite possibly the simplest yet efficient forms for an operative to create such a device. My question being what is going wrong with utilizing the standard NPN and how can it be used in such a fashion.
BREAKS
With the ability for an operative to use such a simple device any misfortunes would be difficult to trace making the "Transistor Timer" a very ideal device. Any help is appreciated.

[nbk2000]

Rarely has so much been said about so little. :rolleyes:

Being excessively verbose doesn't make you seem any more intelligent, just pretentious.

[LibertyOrDeath]

As long as this thread has been resurrected, I might as well mention that the circuit posted looks wrong. Shouldn't it be more like the one in the attachment?

Also, I think BlackfalcoN's right that an SCR would be greatly preferable to a transistor. You want to keep the current flowing through the cap even if the base current is on only briefly or intermittently.

EDIT: Oops, I just realized that the attachment should've been a gif instead of a jpg, but it's not letting me change the attachment. Sorry. :o

[BlackFalcoN]

Here is a visualization of the SCR version, with a cell phone attached instead of a timer.

Any device with a low current beeper/vibrator/buzzer/alarm signal can be used to trigger the SCR.

The switch and LEDs are optional for proper functioning, but greatly improve safety by indicating in which part of the circuitry current is flowing.

Visualization (http://img230.imageshack.us/my.php?image=detnr0.jpg)

[Logic Probe]

To NA: Not enough voltage. If you're using a typical small signal transistor, say a 2N2222 or a 2N3904, you're dropping around .3 - .7 volts (forward voltage) of your 1.5 volt supply across the transistor, even if it is in saturation (maximum conduction). I'm betting that your successful breadboard circuit had more voltage supplied to it. Try the same circuit with a 9 volt battery instead of a 1.5 volt. Even an SCR can have trouble reliably gating at just 1.5 volts. You might also consider placing a capacitor, say 100 microfarad or so, in parallel with the battery to give the output more ampacity.

BTW, BF, I like the added safety features of your circuit, but the SCR and the red LED in the schematic need to be turned around in order to conduct. Cathode has to connect to negative side of source to be forward biased/gated on.

[Charles Owlen Picket]

Let me add something to this subject that you fellows may find of interest. The semi-conductor / IC oriented electronic timer / initiators were actually introduced to the US Military for evaluation some many years ago. (There was a hand grenade that was evaluated.) In industry there is actually a company that manufactures caps that have a small circuit within them.

But the Military rejected the idea. As opposed to industrial concerns, the Military thought them too sensitive to EMP (both in the form of direct pulse weapons & by products of weapons) to warrant a switch from the older standards.

I know the patents for several exist. Some of them are not available (& certainly not to be posted!) but some of them can be found. But the story of the contractual issues are not all confidential. Some of them may be found in archival discussions over the adoption of newer levels of the M26 & later grenades (that time period) if anyone has interest.

Within some of the public patents may be found schematics of direct value to this thread. I don't have the numbers handy but if you know how to search the USPO & use key words such as "electronic, grenade, IC timer, explosive" (not in that order of course, I don't remember what order but that's close enough) you'll find what public stuff is there.

[Logic Probe]

Oh, and I forgot to add, "555's rock!" The 555 is an integrated circuit (IC) that is found in just about anything electronic. Used as a "one-shot" timer, you can make simple, cheap (<$2), reliable timers that can be used in initiators. Just google "555" and "one-shot" and you'll find all sorts of info and schematics available. Use it to gate a capacitor's discharge through an SCR, and you have all the amps you need to heat a small piece of wire hot enough to vaporise.