1Hz Timing Circuit Needed...

[voyager2]

Hi All,
I've been working on my fish lately, and need a 1Hz or 2Hz timing circuit to test the tail with.
I need it to be simple, no ICs, programing, etc.
I have limited time and components.
I first thought of a RC circuit(Resistor Capacitor circuit)but my experience is limited.
All it has to do is swap the polarity of two wires every second(or half second with 2Hz)
I couldn't find anything on SoR, Google, or Yahoo!.
Please help.

Voyager2

[futmacl]

I've been working on my fish lately, and need a 1Hz or 2Hz timing circuit to test the tail with.
All it has to do is swap the polarity of two wires.

If you search for "LED flasher", you will find quite a few 2-transistor circuits around 1-2 Hz - say:

http://talkingelectronics.com/projects/CircuitTricks/images/LedFlasher.gif

That said, a 555 timer configured for 1 Hz (http://sites.google.com/site/uzzors2k/555Tester_schematic-full.jpg) is actually cheaper and simpler - why the aversion to ICs?

Assuming single supply, switching wire polarity for a motor is actually somewhat tricky. At low frequencies, the easiest option is to use a DPDT relay. For reasonably low currents, you could use a miniature DIP relay that costs about $1:

http://www.allelectronics.com/make-a-store/item/RLY-527/5VDC-DPDT-DIP-RELAY/1.html

This is probably cheaper and easier than building a H-bridge (though H-bridge ICs such as FAN8082 aren't too expensive either).

[voyager2]

That said, a 555 timer configured for 1 Hz (http://sites.google.com/site/uzzors2k/555Tester_schematic-full.jpg) is actually cheaper and simpler - why the aversion to ICs?

I don't want to wait 2 weeks for ICs and transistors to ship, I need it now!

Does any one know of a good RC circuit.

Parts I have:
ATmega168s x 5
100uF caps rated at 16v x 10
220uF cap rated at 10v x 1
500Kohm pot x 2
1Kohm resistors x 10
LEDs x 40
MOSFET x 1
Bridge Rectifier x 2

[voyager2]

I'm going to buy one of these:
http://www.sparkfun.com/commerce/product_info.php?products_id=9285
Should help alot!

[amando96]

Get a cheap wristwatch and use the circuitry inside it.

[waltr]

Write a quick piece of code for the Atmega to toogle an output pin.

[Soeren]

Hi,

All it has to do is swap the polarity of two wires every second(or half second with 2Hz)

Then a 2 transistor AMV is the simplest solution - transistors can be chosen for the needed current.

[voyager2]

Get a cheap wristwatch and use the circuitry inside it.

Wrist-watches are not cheap here in Australia!
Since this is just to test the tail, I don't want to spend $20 on a digital watch.

Write a quick piece of code for the Atmega to toogle an output pin.

I'm to lazy to program, that's what I'll do for the finished product.

Hi,

All it has to do is swap the polarity of two wires every second(or half second with 2Hz)

Then a 2 transistor AMV is the simplest solution - transistors can be chosen for the needed current.

What is a transistor AMV?
I am a total noob...

[Joker94]

well given what you are saying all you need is a double pole double throw switch. it is really easy, and that is really all you sound like you need.

2 bucks from dick smiths

[voyager2]

well given what you are saying all you need is a double pole double throw switch. it is really easy, and that is really all you sound like you need.

2 bucks from dick smiths

I need it to do do all this by itself, not manually.

[SmAsH]

Dude, watch from the reject shop - $2-4.

[voyager2]

OK I'll try to find one, that is not: massive, barbie printed or pink

[Razor Concepts]

Arduino? Select the arduino pro 8mhz option and you are set. Really easy code

[voyager2]

I don't have an Arduino, I'm going the squash the $50 robot into it.

[Razor Concepts]

I mean that you have the mega168, so you can run the arduino code on it.

[chelmi]

Write a quick piece of code for the Atmega to toogle an output pin.

I'm to lazy to program, that's what I'll do for the finished product.

The time you spent looking for an "easier" solution would have been enough to write the necessary code...

[Soeren]

What is a transistor AMV?
I am a total noob...

Apparently at using Google as well
Here's a page on Astable MultiVibrators (AMVs) - read it all, you'll learn something.
AMV page

[paulstreats]

I don't want to wait 2 weeks for ICs and transistors to ship, I need it now!

Thats a shame, theres a few real time clock IC's that produce a 1 hertz pulse direct from a single pin (usually used to pulse a second symbol/dot on clock LCD's) aswell as the other useful functions like keeping time and pulsing a pin when a preset alarm is triggered.

[futmacl]

I don't want to wait 2 weeks for ICs and transistors to ship, I need it now!

If you live anywhere near any sort of civilization, it really doesn't take 2 weeks to get two off-the-mill BJTs or a 555 timer.

Also, you really can't avoid stocking these components forever; if you do not have a reasonable library of passive components, transistors, and some of the most popular ICs, you will suffer.

[macdad-]

I first thought of a RC circuit(Resistor Capacitor circuit)but my experience is limited....

For future reference:

Formula for RC circuits:

Frequency = 1/(2*pi*R*C)
R - Resistor Value
C - Capacitor Value

Of course you would still need a semiconductor for the oscillation as just a RC circuit by itself is used as a Low/High pass filter which blocks frequencies above or below the Frequency in the above formula all depending upon the wiring of the circuit.