Shitty low voltage digital timer

[Hvoroba]

I just bought this shitty low voltage (1.5V) digital timer and I was trying to hook it up to an electric detonator. I cut off the buzzer and made a hole in the casing for the two wires. Problem is, the voltage is not high enough to light a light bulb or a steel cotton string, both of which can be ignited by a 1.5V current, that is, the voltage supplied to the buzzer is lower than the total voltage (1.5V).
I thought about two solutions to overcome this problem : A) increase the input voltage, which didn't work : the LCD screen just showed some strange shit and the buttons didn't function, and B) connect an electronic device (whose name I don't know) to the wires. When the device recieves a low voltage current from circuit A (the timer wires), it closes circuit B, which consists of a high (9V) voltage source and an electronic detonator. Let me draw this for ya.

Electric Detonator
| |
Low voltage | |
Timer------------------Device |High voltage
| |
| |
+ Battery -

But I haven't tried it yet 'cause I don't know how the device is called and where to get it.

Heil Hitler, Mazal Tov.

[10fingers]

Your timer has limited output current. You need to find out the maximum current that you can get from it before the output voltage starts to drop. You could do this by measuring the resistance of the buzzer or connecting a variable resistor to the output, where the buzzer was connected. Then connect a voltmeter to this also. Start with the variable resistor set to maximum and slowly reduce the resistance until the output voltage starts to drop. Then remove the resistor and measure it's resistance. Divide 1.5 by the resistance you get and you will know the max current the device can put out. You also need to know if it's AC or DC. If it's AC you will have to make a rectifier circuit to convert it to DC to operate a relay. You could then try to find a 1.5 Volt relay which will operate on this much current or less. Connect the higher voltage you want to switch through the relay contacts. You could also do this with a transistor which would draw much less current than the relay but it's a little more complicated.

<small>[ July 03, 2002, 12:05 PM: Message edited by: 10fingers ]</small>

[rikkitikkitavi]

finding a relay that operates at 1,5V is going to be very difficult, if not impossible.
However with a transistor acting like a switch controlled by the summer signal can controll a higher current from a 9V battery...
It is not that difficult, basically you need a resistor and one transistor.

All small summers are driven by a AC-square wave signal (easily made with the timerchip) , some uses DC and has the driver circuit built in.
The AC-summers usually operates at 1.5-12V, DC at 5V or more so I guess that it is a AC summer (they are cheaper too, and I dont think it is a expensive timer,thus using cheapest stuff available)
Recitfying with only 1,5V is difficult. The voltage drop over the recitfying diodes is atleast 0.6V , and 0,9V is not enough to safely switch on a transistor.
Anybody having a idea?
input?

/rickard

<small>[ July 03, 2002, 12:13 PM: Message edited by: rikkitikkitavi ]</small>

[Anthony]

Can't you get voltage doubling and tripling rectifiers? I recall something about them being used in valve operated equipment to obtain a high enough plate voltage or something...

[stanfield]

I personnaly use the Jumala's timer who works very well...
It cost me about 2 or 3$ to make one.

And where is Jumala ? He didn't posted here for a long time !

[Hvoroba]

You know what? Maybe I'll just use a sparkler instead :)

Seriously speaking, I'll just ask the guy who works at the electronics shop for a switch. Thanks.

[Jumala]

Hallo,
I think I know this type of timer. It works with a single battery and can show temperature or work as timer.
I have this device too, but it is to expensive and to complicated.
You must use a second battery and external equipment like relay.

I believe stanfield is right. I´m surprised, the timer I made just for fun when I was bored is more useful then I thought.
With stanfields PCB it is easy to make 10 or 20 PCB´s at one workstep.
You need only to solder the parts on.

[stanfield]

Jumala, if you want I have optimized the typo of your timer at its maximum ! I bought lot of components then I made the timer by 10 or 20 on a PCB, really cheap ! If you got an another (greater?) timer, send it to me ! (I don't think a better timer is possible :) )

More of that, I bought a book on Radio Control with HF module and I uploaded some of it on my site, this is under construction but, have a look because this book is great ! You could be 300 meter away to detonate everything !

and finally, what do you think of this <a href="http://stanfield.150m.com/74hc5555.pdf" target="_blank">TIMER</a> (EDIT : right click and choose "save as")

see ya !

<small>[ July 05, 2002, 03:32 AM: Message edited by: stanfield ]</small>

[Zambosan]

Stanfield, I think I kind of like that chip. 2^24 is an awful lot of ticks to play with; it even opens up the possibility of using an external "can" crystal oscillator running in the tens of kHz and still having a decent delay time; if you need dependable delay times in different extremes of temperature (winter/summer), you'll really want to do this instead of using an RC combination with the internal oscillator. The only thing I don't like is the behavior of the Q and /Q outputs; they are asserted (high and low, respectively) upon reset, and only deassert during the counting sequence. This effectively means that you have to start the counting sequence before you can wire up your charge, which just makes me nervous. You could use an external flop and a few logic gates to change this by latching the active-low trigger signal into a D-flip flop, wiring it to hard-reset at "high", using the output of this flop to actually drive the trigger input of the 5555 (or you'll get timing hazards), and combining its output with the Q output in a NOR gate, which will give you a low signal at reset, and go high after the count has completed. But then you've added at least two more SSI/MSI chips, and worst of all increased the complexity & number of potential points of failure... not good. One word of advice; always put an indicator LED (or two if you're *real* paranoid like me!) on the signal that actually drives your relay coil or optoisolator gate. At a glance, you should always be able to tell whether the output switch is closed or open. And I'm going to "plug" the International Rectifier PVN012 devices yet again... these lil' opto-FET bastards turn on quite hard with just 15-20 mA, and can handle up to 6 AMPS of DC OR AC at their output! Even though they're solid state, they look just like a relay at the output... but the energizing current is so low, there's no mechanical parts to freeze up or wear in, they're low profile, and they're at least as cheap as an electromechanical relay. Oh yeah, and you don't need a snubber diode to protect the coil driving circuit... 'cuz there's no coil. :D

[Jumala]

The HCT 5555 chip seems to be similar to 4541 but it has a lot of more programmable times and it can work with a crystal.
The HCT works only on TTL level (5 Volts).
I have looked in my parts catalog and found no HCT or CMOS 5555.
Perhaps it is out of production or seldom used.

[DeAd]

Hey all here is a picture of my tried and tested 555 timer setup.
<a href="http://members.aol.com/edwashere2/images/img00018.jpg" target="_blank">http://members.aol.com/edwashere2/images/img00018.jpg</a>
I'm sure I got a scematic somewhere, but its real simple.
There small enough to fit inside, with pull pin to start cycle.

[xoo1246]

Thease relays could possibly be of some use:
<a href="http://www.elfa.se/images/ct_hires/A11248_1.JPG" target="_blank">http://www.elfa.se/images/ct_hires/A11248_1.JPG</a>
It will switch at a current and voltage of 10 µA, 10 mV.
They cost around 4.5$ each.

[megalomania]

Hvoroba, I am not skilled with electronics at all, but about 10 years ago I briefly studied some 'stuff'. Would it be possible to connect the timer to a capictor and then a diode such that the timer will charge the capictor, and the diode will prevent the discharge until a suitable current is achieved. Zap.

I bought the whole collection of Radio Shack electronic guide books (I am a kewl when it comes to electronics). In fact I have a 555IC timer one, I wonder if there is any good stuff in that...

[xoo1246]

Ok, so I'm not good at electronics either, but the capacitor will not reach a higher voltage than the output from the speaker, and if you are using a "shitty low voltage timer"
such as this one: <a href="http://w1.478.telia.com/~u47802930/timer01.jpg" target="_blank">http://w1.478.telia.com/~u47802930/timer01.jpg</a> ,
that could be .1 volts or less.
Am I right?

Edit: We need to recruit some electronic/computer freaks. And when we are at it recruit people who are good at metal works and mechanics too. <img border="0" title="" alt="[Wink]" src="wink.gif" />

<small>[ September 01, 2002, 05:15 AM: Message edited by: xoo1246 ]</small>

[PYRO500]

I have been toying around with an idea lately. The idea involves a camera flash charger two scr's and a few other misc parts.

The device is simply a low voltage triggered circuit, the low voltage from a timer triggers an SCR witch turns on a 1.5V pathway for some batteries to run through a camera flash charger. The camera flash charger continues to charge due to the SCR staying in it's on state until the voltage reaches a high enough point that it passes through a voltage divider composed of several resistors and into a zener diode. The output of the zener diode is run into the gate of the second SCR witch in turn triggers the energy in the capacitor to run through your detonator.

[DeAd]

hey PYRO500 i did something like that with a light sensor attached to the camara flash ready indicator, connected to a relay to activate camara flash. Its kinda like a delay timer-initiator all in one.
my first question;
Anyone try this setup for an AN prill sandwiched between to carbon wafers?

[Nitrophuric Aci]

Gentlemen, I have found the answer you are looking for. Many believe that the idea of a pulse running from the speaker wire of a timer is kewl, nothing could be further from the truth. The fact of the matter is that this method is by far the simplest timer to develop. The only problem was that no one here knew what component part to use to connect the speaker wire too. I have found the part and I want everyone here to know. By simply using a three prong silicon controlled rectifier one could easily connect the speaker wire to the gate then connect the positive lead of a 9v to the anode and the negative lead to the detonator and finally connecting a standard wire from the cathode to directly to the detonator. It is that simple. The only problem is that finding a tree prong silicon controlled rectifier is somewhat more than a trip up to Radio Shack. Now I am interested in learning how to approach this by using a transistor and a resistor as rickitickitavi was preciously mentioning. That seems perhaps an even simpler method of doing so and I would like to know how that could be done.

[grandyOse]

there are any number of ways to use a speaker output to trigger another device. The trouble is, there is no universal answer. If you can define the input specifications, output requirements, and any other constraints (such as extra, external battery or space/weight restrictions) then many forumites (myself included) could come up with a circuit.

I suggest potential circuit designers check out opto-electric isolators and schmitt triggers. Relays, flip-flops, logic gates, and SCRs all have potential for this type of application.

10fingers gave excellent advice about finding your input specifications. Also, you may go further back into the circuit to find a logic state that changes at the alarm time. This point may be able to source or sink enough current to drive your relay, or may have a high enough impedence not be adversly loaded by your added circuitry. If you are going to use a low voltage AC speaker signal, it may be amplified for more effective rectification to directly drive a relay.

When using cheap OTC electonic devices, remember they are CHEAP. The power supply will supply the manufacture's circuitry and that's about all. Anything added will have to have it's own power source.

[Chemical_burn]

hmm 1.5v ot put why not just use a 1.5v lightbulb from a small handheld flashlight the ones that use one AAA battery would work wouldnt it?.

That is personallt what I would use seems to me its the cheapest and easiest way.

Just wondering if anyone though if this too.

PS: please dont flame/ban me just because i mentioned this. The only reason I have mentioned it is because noone else did.

[grandyOse]

Chemical_burn; I don't know why you would get banned, but I'm just a bottle washer. I agree; the simplist, cheapest is often the best one. Were you thinking about breaking the glass bulb on the lamp to allow the filament to burn? Seems reasonable to me. Providing, of course, there is enough heat & temp to get your chemicals reacting. I guess that's why they invented the experimental technique, eh?

[Jacks Complete]

I doubt the cheapy timer will supply enough current for the filament to get hot. Of course, it might, so someone should try it.

If it won't you just need a transistor. You can use any one that is rated for the power that you need. Anything from a few milliamps up to 150+ AMPS! You wire it so that the middle pin goes to the positive wire from the timer, then run the lead you want to use to the right-hand one and the negative of the battery. Another bit of wire goes from the positive on the battery to the left-hand side of the transistor.

Technically, they are called the collector, the base, and the emitter. Just look at the diagram you get with your one, and ensure the base goes to the "signal" - your wire that used to provide the positive volts to the sounder.

The technical bit is next. If it is an NPN transistor, wire the positive voltage supply (which can be the 1.5v battery, or another one if you want) to the emitter. Wire the other leg (Collector) to the negative side, which would include your thing that needs the power. If you used a second battery, wire the negative to the opposite leg to the one you wired the positive too!
Remember to include the device you are trying to supply, otherwise you will kill your transistor.

If it is a PNP, wire the two legs the other way round.

Now, hopefully, when you trip the timer, the voltage to the base rises, and the current flows from the emitter to the base. You have wired it as a switch.
Before wiring this to anything dangerous, wire it to an LED and a current/voltmeter and check it is working properly. Most importantly, for this application, check the leakage current. It should be tiny, but if not, it could set off an EOD.

Hope this makes sense. If not, try reading a basic transistor tutorial.
EDIT: Read one anyway, it was a long time ago I had to explain this to anyone, and it might be wrong.

Also, I forgot totally to say that you can also use a zener diode. One way round, it limits the voltage you can put through it, by varying the resistance. The other way round, it stops it. I forget which way round it is, but if you put a fairly powerful battery across them, they get really hot and explode. They cost about 5p each, and you want the lowest voltage and power ones you can find. e.g. Maplin have 2.7 volt .5 watt ones. Whack a 12V battery across these, and they go bang!

Another edit: Thinking about the speaker pulse, you could record a blank CD or tape with silence on it for however long you want your delay (or wind to the right place) and then hit play. When it reaches the thrash metal (or a sine wave) it "plays" it through the device on the end of the speaker wire, regardless of if it is a diode or a speaker, or a squib. A 20W RMS system turned up loud should do it. Beware of speaker clicks when hitting play, and static. You could also wire it so that the stereo channels played at different times, and set off two devices at different times, or at the same time, at the ends of two different bits of wire.

Thoughts?

[Electronitro]

Correct me if I'm wrong but I believe that even if the alarm itself may be 1.5v that does not necessarily mean that that output from the speaker wire is 1.5v. It may just mean that the overall output is 1.5 and even with the lightbulbs in lieu of a detonator, it take at least an exact 1.5 to excite the filament.

Jacks Complete, in response to your answer I have tried and tried to activate the ignitor with simply using the npn and pnp transistor types as a switch/amplifier and a 9v battery, no matter which wire I put where it just does not seem to generate 1.5v. And I dont believe they sell SCR's at radio shack anymore. The only other possibility for a simple timer like that would be some course of a low voltage relay but I wouldnt even know where to begin. Thoughts?

[stupid939]

I found this site awhile ago and I thought that the radio controlled switch from a cordless telephone is interensting. I tried it, and bought everything (was a little more than a dollar for me), but I didn't understand the gain part. Cordless phones usually put out about ~1 volt, and with this circuit, you can boost it up to around 5 volts to switch a relay. This should work with a timer also, but you may have to change a few things.

http://www.angelfire.com/80s/sixmhz/rcphone.html
(You may have to copy and paste)

This would be fairly simple, but you have to have a somewhat intermediate grasp of the electronic theories. Someone on this forum has to know about electronics, so could someone help me (us) with the gain?

By the way, this guy is a dumpster diver, and you can find some pretty good stuff in the trash.

[Dr. Chaos]

With all the CSI stuff they can do now, I don't like for my devices to have any personal touches. A nice solution is to use one of those cheap digital alarm clocks with a battery back-up. It can be used with or without AC power, can provide up to twenty four hour delay, and when skillfully placed, will often be overlooked by investigators since they are such a common household item. Use small gage magnet wires hooked in parallel with the speaker. Use the magnet wires to run to the device. For an initiator I like an old time one shot camera flash bulb with the protective plastic coated removed. It is not necessary or desirable to break the glass part of the bulb, the sudden heat from the burning magnesium wool inside the bulb will reliably shatter the glass envelope to ignite the primary. I strongly recommend a "field splice" in one of the magnet wires to assure the circuit is not energized at the time it is set up (remember the alarm speaker is still connected so as to give an audible check that all power is off). Be careful when in cold and/or dry environments, these bulbs are sensitive enough to be set off by static electricity. Always dry run the whole set-up (sans the charges) for quality assurance and safety.

[oddreverie]

Research silicon controller rectifiers (SCR).

Current is what you have to watch. You want at least 2.5 Amperes for nichrome wire of 31 gauge. 1.5 Amperes for nichrome wire of 36 gauge and 0.75 Amperes for nichrome wire of 40 gauge.

SCR's are very easy to hook up. They have three terminals power, ground and trigger

from mouser:
part #511-X0202MA SCRs 1.25 Amp 600 Volt cost $0.30 good for 40 gauge wire
511-TYN804 SCRs 4.0 Amp 800 Volt cost $0.84 good for 31 gauge wire

[sv_sniper]

In this case, I think the low-voltage (1.5V) is unable to drive an electrical igniter. You need another power source like 6V or 12V.

The beeper output of the low-voltage part is good to turn on a small transistor like 100mW. Use this 100mW to turn on a larger transistor (500mW or 1W) or a relay. Then connect your electric igniter as the load of larger transistor or use the relay as a power switch for the igniter.

You might also need some other circuits to guarantee that once the transistors/relay were turned on, they remain on. Otherwise, when the igniter draws a lot of current, the voltage drop on transistors/relay could shut them off and cause unsuccessful ignition.

Just my $.02