Simplest timer

[Hero999]

They need to:

1. Stop selling Crappy products.
2. Start selling hight quality products.
3. Stop selling things at rip-off prices.
4. Start selling thigs at reasonable prices.
5. Sack all their brain dead staff.
6. Employ decient staf who actually know something about electronics.

Well I don't know about Radio$h@g as they left the Uk a few years back but Craplin's need to do all of the above.

 

[busines5]

Hi,

Have at look at the following link, it gives a very detailed account of the 555.

It also gives some simple diy circuits including a 10 min timer - just what you want.



hth

Yes, I found that page a little after posting on this board. It says all that's needed to make the simplest timer is a 555 timer, a resistor and a capacitor. And I believe I can change how much time it will countdown or up by using resistors and capacitors with different values. That's good.. I'll play around with different resistors and capacitors once I figure out how to hook it up. BUT, I need some help there. I can't seem to figure out those diagrams, like **broken link removed** that belongs to that simple timer I just mentioned.

Here's what I think I figured out so far from that diagram..

I take the red wire from a 9V battery clip and connect it to pin 8 of the 555 timer. I take the black wire of the battery clip and connect it to pin 1. I connect a wire from pin 3 to one of the legs of my electric match and connect a wire from the other leg of the match to the black wire of the battery clip. Now the rest I just don't get. It looks like there's a wire connected to the red wire(from the battery clip to pin 8) that connects to a leg of the resistor. (Does it matter which leg?) Then from the other leg of the resistor it goes all the way to the positive leg of the capacitor(I assume capacitors are to be hooked up the right way) and it looks like wires from pins 6 and 7 are hooked up to it along the way. Then we connect a wire to the negative leg of the capacitor and connect it to the black wire of the battery clip(or 'ground' if you will).

So how's my aim?
Go easy on me, ok

 

[audioguru]

You are almost correct.
1) The max allowed output current from a 555 is 200mA. Your "electric match" might draw more which needs a power transistor to handle the high current.
2) You must trigger the timer by causing its trigger input pin 2 to go low for a moment. You also must make pin 2 high when it is not being triggered.

 

[richard.c]

Please see you PM box.

 

[ramoni]

hey pals, show me adiagram for a timer without using 555, could you?

 

[audioguru]

Timers:
10 Charge a capacitor from a resistor and use a FET-input opamp to measure the voltage rising.

2) Charge a capacitor from a resistor and use a Scmitt-trigger Cmos gate or inverter to switch when the threshold voltage is reached.

There are probably many other ways to make a short timer.

A long timer is made with an oscillator/counter IC like a CD4060 or a CD4541.

 

[RetiredHAL]

Hi, I stumbled across this thread "googling" Kitchen timers ccts.
I don't want to appear paranoid, but what is "busines5" trying to do here ? Make a simple 10 minute delay to fire a rocket or set off a bomb. He is obviously completely ignorant of any electrical or electronic knowledge and is asking to be spoon fed how to start from scratch. His opening post wants a simple circuit to fire a rocket after 10 minutes. ??????? How far away does he want to be before firing the rocket?

Cheers RetiredHAL
PS Nice Site

 

[audioguru]

A single 555 doesn't make a delay for him to run far away before his diy rocket explodes. Its output goes high immediately when the button is pushed.
The timing of a single 555 is how long its output stays high after being triggered.

He needs a second 555 to be triggered when the first 555 times out. Then the second 555 drives a power transistor that lights the electric match.

 

[RetiredHAL]

Hi, audioguru, you are right, about needing more parts than one 555 ic.

My point is, that to ignite a rocket (and I presume this to mean fireworks) you light the 10 sec fuse which is luckily attached to the rocket when you buy it and move away 15 metres and watch it go up in the air. I have problems imagining where one would want to set up a rocket, press the button and wait 10 minutes to see it ignite!!!

Cheers
RH

 

[EvilGenius]

Triggering a rocket with a timer...

Hi boys and girls.

Not to make things more complicated but I saw a simple and cool timer circuit for rockets using 555 timer and 4017 and a few more parts. You can adjust the time with a variable resistor and connect the outputs of 4017 via resistors to drive 9 LEDS (7 green, 1 yellow, 1 red, and last bit for boom. That way you can actually see the timer in action and prepare for it (day or night). There was also a safety switch used in series to the main positive feed to shut down the whole thing just in case.

By the way they sell all sorts of kits similar to this idea cheap online if you search for it.

Cheers

 

[EvilGenius]

10 Step Rocket Triggering System

Here Is A Diagram Of The Above Mentioned Circuit.

 

[Hero999]

Or better still use a CD4060, only one IC.

You could use a micro but that would involve programming.

 

[k7elp60]

Here Is A Diagram Of The Above Mentioned Circuit.

I can see one error on the schematic. Pin 2 is connected to pin 1.(If you follow the line from pin 1 down to the capacitor connected to pin 5 there is a junction point that shows pin 1 connected to pins 2 and 6. This wrong. Take the junction dot off.

 

[EvilGenius]

Correction on schematics...

Thank you for bringing that to my attention k7. That was not meant to be a connection node there. By moving some parts it moved the node as well. This new schematic will address that. As you can see the node is now moved back where it belongs to the lower capacitor off pin5. Again Thank you sir!

To Hero: I have never used cd4040 or cd4060 are these chips Johnson counters with self clocking (do not need external clock or xtal)?

 

[audioguru]

A CD4040 is just a binary counter. It can divide an external clock signal by up to 4096. Its 12 outputs are the clock divided by 2, by 4, by 8, by 16, etc.

A CD4060 has an RC or crystal oscillator and a binary counter. It can divide its clock by up to 16,384. Its counter does not have all binary outputs available.

A CD4541 also has an RC oscillator and a binary counter. It has automatic reset if you want or not and it can stop at a certain count if you want or not.
Its output is selectable to be high or low.

Other timer ICs are available. One has a monostable output.