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how to measure frequency in this circuit? Answered

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i want to measure the frequency of this flasher circuit but i always get a frequency close to that of the mains. I am using a wall wart.
i changed some of the components to speed up the flashing but the frequency reading stayed the same.
to check my multimeter i tried measuring the frequency of mains and the joule thief circuit and it looks like my multimeter is good.

how should i measure the frequency in this flasher circuit?

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MarkP64 (author)2015-10-20

Sorry to add a comment on an incredibly old thread, but
could someone please help determine how to calculate the frequency of the
flashing LED in this circuit diagram?

I would have thought it was something like
0.693*330,000*.00001 = 2.28 flashes/seconds.

But when I make this circuit in Yenka, it comes out to be
more like 1 flash/second.

There is a very similar circuit at the following website
with an explanation of how the circuit works but no timing calculations.

http://www.talkingelectronics.com/projects/FlasherCircuits/Page83FlasherCircuitsP1.html

thanks

Mark

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lemonie (author)2011-09-25


How are you measuring ~60Hz then?

L

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codestroy7 (author)lemonie2011-09-26

i measure the frequency across the LED and it always give 60Hz

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lemonie (author)codestroy72011-09-26


How? You've asked how to measure frequency, but you say that you're already doing it. Do you doubt that the measurements which you get are correct?

L

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Re-design (author)2011-09-25

Change to battery then measure again.

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steveastrouk (author)2011-09-25

Get yourself a cheap oscilloscope - you really can't do serious work without one eventually.

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rickharris (author)steveastrouk2011-09-25

Aren't cheap and oscilloscope mutually exclusive? :-)

Although I was able to sort out my RC transmitter with a free offering using the PC sound card. Seemed to work within it's abilities. Not much bandwidth though.

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rickharris (author)steveastrouk2011-09-25

Things have got better now even I could afford that.

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rickharris (author)2011-09-25

Across the LED should give you a realistic reading but you can work it out.

The frequency is controlled by the capacitor and the resistor that discharges/charges it.

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codestroy7 (author)rickharris2011-09-25

yah i know... the circuit is working...

i tried to get the frequency across the LED but i get nearly 60Hz which is impossible since the LED is not visually flashing that fast i suppose i am getting the frequency of the mains.

at some point i changed the flashing speed of the LED so i am expecting a change in the frequency reading. but the reading is still 60Hz

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frollard (author)codestroy72011-09-25

Add a smoothing capacitor - your 'dc' wall wart is spitting out bumpy dc with ripple, and your meter is detecting that ripple.

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codestroy7 (author)frollard2011-09-25