I am interested in setting up a 555 timer for extremely long pulse times, 15 minutes. Also, an AC output, one positive square wave pulse followed by one negative, etc. How much of a problem is leakage from capacitors with such extremely long delays? I have to make this simple. Thanks for your time. Any help would be appreciated.
555 Timer Question
Dec 22, 2005
28 Replies
Thanks very much! I will look at it in just a moment.
Yes, that's what I mean. I am not fluent in electronics (Sorry!), but I can build simple circuits from a schematic. I am also curious if the audio output from the headphone jack of a CD player can be inputted to the circuit and modulate these pulses. Is that possible? Thanks very much for your time. I appreciate it.
Considerable. What kind of accuracy are you looking for?
This question just came out in January 2006 Nuts & Volts
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issue, page 13. This article is not on their website yet so if you want me to I can draw up the schematic they have in the magazine. They use a 4060 ripple counter IC, resistors (4.7M, 330K, 1K), pot (100K), 68uF cap, 2N3904,
1N4001 and a relay... fairly simple circuit....
From the article :
"The 4060 includes an oscillator whose frequency is set by two resistors and a single capacitor. When the oscillators frequency is at 18.2 Hz, the Q14 output (pin 3 of the 4060) will toggle on and off every 15 minutes... the
100K pot is for fine tuning the timer."The relay will control what you want on or off...
This should take care of the "timing" issue you are needing...
Hope this helps a little or sparks an idea...
Dave
Here is the schematic...
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Like I said, pretty simple...
On your AC output... are you meaning "one positive square wave pulse" for 15 minutes?? (positive voltage for 15 minutes) Then a negative square pulse for the next 15 minutes??? (negative voltage for 15 minutes) ???
Need to explain this more.......
Dave
What kind of voltage are you wanting to use?? 12v - 9v - 120v?? on the outputs? What are you wanting to run?
Dave
9 volts.
This 4060 timer chip, is it also known as M54HC4060? Thanks.
Yes, that\'s a military version of it.
Why make it so hard?
Just use the relay connected to the transistor connected to Q14 of the 4060:
+V | +9V -9V +--------+ | | |A | O--> / +/-V OUT C 4060 Q14>--[R]--B E | +--------------------> GND
John Fields
Professional Circuit Designer
Yes. If the + and -9V were batteries they\'d would look like this:
(View in Courier) +V is just the voltage to operate the relay, and
if it were a 9V relay the + 9V could be used to energize it during
the times +9V was supposed to be the circuit\'s output.
+V
| +9V -9V
+--------+ | |
|A | O--> / +/-V OUT
C |+ |
4060 Q14>--[R]--B [BT1] [BT2]
E | |+
| | |
+----+----------+----> GND
I don\'t know. That is, those pages went dead and I can\'t get back
to the schematic. If you switched them through a transistor they\'ll
need diodes, if you\'re using another relay to switch them, then
generally, no.
Not exactly sure... the article only says "4060 Ripple Counter"
Here is an update on the schematic... I added some relays to control the output switching...
This should work.. no guarantees because I haven't built it to make sure it would work :) .. logically and on paper it should...
I have made 2 schematics, one showing the positive cycle
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and one showing the negative cycle...
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You will notice that with each 15 minute pulse of the 1st relay, the other 2 relays will switch polarities on the output you are needing switched... giving you the cycling you wanted... +9v for 5 minutes then -9v for 15 minutes then back to +9v for 15 minutes and so on....
Hope this helps Dave
Hey John,
Thanks for the input as I am also learning... :)
I'm a little confused on how this would work? With how you have it, wouldn't you have to supply a -9v so it would switch between the +9v and -9v with just the one relay??
Sorry if this is elementary but my "little" brain only came up with what I had with the relays... LOL Can't seem to comprehend what you are describing...
The top 3 voltages ( +V , +9 and -9) in your drawing above, are those the "supplied" voltages??
Dave
Thanks for clearing that up John... I was taking it (what they was wanting) as using just one supplied voltage of +9v... the relays would then do the switching from neg. to pos. ...
Either one would work I guess, yours is much simpler but requires 2 separate supplied voltages...
Thanks again John
Dave
Oh, BTW.. if they were to use the 3 relays as in my design... would the 2 other relays need diodes also?? I missed that before I uploaded it....
Dave
Thanks John... Yea, my hostings server went down I guess... still not up.. grrr...
Anyway, they were coming off of the 1st relay so I guess they don't need them...
Thanks again John.. Dave
It depends on what he\'s going to do with the output signal. Your
way requires a floating load, (that is, the load can\'t be grounded)
while using two supplies lets it be grounded if necessary.
BTW, I went over to that page again (it was up this time) and it
struck me that by using a DPDT relay as the relay being switched by
the transistor and your circuitry to do the polarity reversal into
the load, both of the other relays could be eliminated, like this:
+9V
|
+----+-------------------------+
| | |
+--------+ | |
|A | O--> / /OUT
C | |
4060 Q14>--[R]--B +------------------------>OUT
E |
| |
+-----------------+
|
GND
:-)
The cathode of the diode should go to +9V:
+9V
|
+----+-------------------------+
| | |
+--------+ | |
|K | O--> / /OUT
C | |
4060 Q14>--[R]--B +------------------------>OUT
E |
| |
+-----------------+
|
GND
Sure.
Now see, I knew there was a simpler way to make the one I designed.. LOL I just couldn't come up with it... The thought of using 1 DPDT relay had crossed my mind but I wasn't seeing how it would work...
Now I do...
Thanks John for helping me out ... I'm planning on building a few projects of my own during the next year.. I graduate in December 2006 .. will be getting CET certified, J-Standard certified, A+ certified, FCC licensed and certified...
I will probably be asking you some design questions in the future, If it's ok?
I know I can just go out and buy these things but I think I would learn more and have more satisfaction if I attempt to build them... Here is a list of things I'm going to ATTEMPT to build.. LOL
Power Supply (fixed plus variable voltages) DMM Freq. Counter Soldering station Small Power Amp (stereo) AM/FM Radio Function Gen.
just to start with...
Thanks again for your help... looking forward to talking to you again...
Dave
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