Author Topic: Fastest 555 Timer cycle  (Read 7404 times)

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Offline Spoil9Topic starter

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Fastest 555 Timer cycle
« on: August 09, 2008, 09:24:20 AM »
I'm looking to convert 12VDC into AC for use in a wireless power transmission experiment.
I'm looking to use a 555 timer cause it's simple and I'm not the smartest of the bunch or have the biggest budget.
I have looked on line and found that the higher the freq. the better the effeciency of the mutual inductance at a distance, so I'm looking at the thousands or tens of thousands Hz. Can a 555 timer cycle this fast?
If not, what are my options?
Long term would be to put something like this on a motorcycle so that when I hit the brakes 12V is sent to a reciever on my helmet which would power LEDs to act as a remote 3rd brake light.
I know they make stuff for this (I have one on my helmet now), but they all require batteries to power the LEDs. The one I have uses 4x CR2032's which runs into money when I need to replace them. Using this idea, no batteries would be needed.
Thanks.
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Offline steferfootballdude13

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Re: Fastest 555 Timer cycle
« Reply #1 on: August 09, 2008, 10:02:24 AM »
I'm looking to convert 12VDC into AC for use in a wireless power transmission experiment.

Are You trying to transmit Current through the Air?

Can a 555 timer cycle this fast?


I'm Don't think it can, never tried, but 555s usually send out DC pulses measured in seconds or fractions of seconds (to make an LED blink or something.) DC to AC converters are more difficult than AC to DC. If nothing else you could buy something like this: http://www.dcacpowerinverters.com/itemdesc.asp?ic=PW1100-12
It is for 12 V DC; however i doubt that you need 1100 Watts for 5 LEDs.

If not, what are my options?

If you send enough current it might jump directly to your helmet.... Kinda like a lightning Bolt :o
Other than that I would suggest reading into this: http://en.wikipedia.org/wiki/Wireless_energy_transfer Under the "Low Power" sub topic, It talks of a company: Powercast Doing just that (wireless energy transfer) for 6 v.

EDIT: i realized i asked a question he answered.
« Last Edit: August 09, 2008, 10:06:57 AM by steferfootballdude13 »

Offline dsheller

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Re: Fastest 555 Timer cycle
« Reply #2 on: August 09, 2008, 02:28:36 PM »
555s pulse a square wave, and are capable of several thousands of hertz, but their output current is very low. Not sure if you could hook it up to a switching transistor to amplify the current, never tried it. But from what I remember most of the wireless transmission was done with microwaves... so good luck with that =)

Offline izua

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Re: Fastest 555 Timer cycle
« Reply #3 on: August 09, 2008, 03:38:05 PM »
you can hook up the output of a 555 to drive a bipolar transistor stage (NPN + PNP) in a darlington array, which woudl reduce frequency but increase current output.
Check out my homepage for in depth tutorials on microcontrollers and electronics.

Offline Soeren

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Re: Fastest 555 Timer cycle
« Reply #4 on: August 09, 2008, 10:01:38 PM »
Hi,


The 555 has an upper limit of ~500 kHz.
Regards,
Søren

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Offline TrickyNekro

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Re: Fastest 555 Timer cycle
« Reply #5 on: August 10, 2008, 02:07:12 AM »
I don't know if you use a crystal resonator for this although if we are talking for short distance you may need something at GHz area...

Anyways, have a look at Tesla theory.
Tesla was for wireless power transmition... but he though air (ionoshpere)
and ground as the two poles of a battery...

Get to play with tesla coils and you may not need that much of a frequency for just experimenting... cause in high freqs you may have other problems...

Also consider your mosfets and not transistors.... you gotta get a fast response one...
Not a big deal but have this in mind... Many of them switch state at a matter of nanoseconds....

In the end if you can get a 555 emu so you can see what kinda circuit you need...
555 timer is a good program if I remember right...

Best regards, Lefteris
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Offline Spoil9Topic starter

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Re: Fastest 555 Timer cycle
« Reply #6 on: August 11, 2008, 09:37:29 AM »
steferfootballdude13:
Yes, thank you, but I have read that already. Wikipedia and Google are 2 sources I go to before I post questions here. In this case, I have also read Teslas Biography "Man out of Time" while I was last deployed and feel it has opened my eyes to a lot of things.
I would like to stay away from converting up to 120V AC as I think that is wasting a lot of power to jump that high just so I can bring it back down to power LEDs on the helmet.

dsheller:
Did not think of using transistors in this case but I will look into that shortly.
There are several articles about MIT doing this research. They were able to power a whole room wirelessly. Only their coils were 2ft in diameter and I'm looking for something like an inch or two. Of course they went across a whole room and I only need a meter.
http://www.technologyreview.com/read_article.aspx?ch=specialsections&sc=emerging08&id=20248&a=
http://web.mit.edu/newsoffice/2007/wireless-0607.html

izua: No idea what you're talking about but I will google it to learn more.

Soeren & TrickyNekro: Thanks and I have to learn more about mosfets as well.

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Offline Admin

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Re: Fastest 555 Timer cycle
« Reply #7 on: August 23, 2008, 07:28:01 AM »

Offline Spoil9Topic starter

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Re: Fastest 555 Timer cycle
« Reply #8 on: August 28, 2008, 09:31:39 PM »
I just started school again and I totally don't have the time to mess with this idea. I still believe that it is possible for the short distance that is needed, I just don't have the time now to mess with it now as I'm trying keep up with classes and ride the motorcycle while it's still nice out.
I don't know where everyone is at, but Chicago winters suck sometimes.
Thanks again for every one who posted info as I as still reading over everything trying to learn all that I can.
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Offline dsheller

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Re: Fastest 555 Timer cycle
« Reply #9 on: August 29, 2008, 12:02:55 AM »
...

dsheller:
Did not think of using transistors in this case but I will look into that shortly.
There are several articles about MIT doing this research. They were able to power a whole room wirelessly. Only their coils were 2ft in diameter and I'm looking for something like an inch or two. Of course they went across a whole room and I only need a meter.
http://www.technologyreview.com/read_article.aspx?ch=specialsections&sc=emerging08&id=20248&a=
http://web.mit.edu/newsoffice/2007/wireless-0607.html

izua: No idea what you're talking about but I will google it to learn more.
...

Izua was talking about the same thing I was except he took a step further and told you to use a Darlington Pair (these come in their own packages now, but you can easily build one with two BJT transistors). Darlington pairs provide very very high current gain, but, as Izua said, decrease your frequency.

 


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