How can I use a timer 555 IC to obtain a frequency multiplier? I made a frequency divider by using a timer in monostable mode but a multiplier looked difficult. Can somebody tell how can I design a multiplier?
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1\$\begingroup\$ A 555 in monostable mode is NOT a frequency divider. It does not track the input frequency it simply ignores the input for the time of the monostable. In the same way, the 555 is inappropriate for use as a multiplier. \$\endgroup\$– Jack CreaseyCommented Sep 19, 2018 at 15:26
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\$\begingroup\$ What I meant was that it becomes a divider when the trigger frequency is higher than 1/(1.1RC) and not the normal monostable case \$\endgroup\$– user172541Commented Sep 19, 2018 at 15:39
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\$\begingroup\$ That still doesn't make it a frequency divider. What you describe is a "one shot" circuit. \$\endgroup\$– BimpelrekkieCommented Sep 19, 2018 at 15:57
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\$\begingroup\$ Do yourself a favor and read a book on PLL's. There are plenty of texts, but one notable free text is from TI: ti.com/lit/ug/snaa106c/snaa106c.pdf Well worth adding to your library. \$\endgroup\$– Jack CreaseyCommented Sep 19, 2018 at 18:36
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\$\begingroup\$ The link above in @jack-creasey's comment is expired, but here is an updated link: ti.com/lit/ml/snaa106c/snaa106c.pdf \$\endgroup\$– FoneboneCommented May 7, 2021 at 4:24
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2 Answers
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Something like this could work for a multiple by two of a 50:50 square wave at a specific frequency.
simulate this circuit – Schematic created using CircuitLab
The X-nor gate produces negative-going pulses on each edge of the input. The 555 produces an output pulse for each edge. Set the astable width appropriately.
answered Sep 19, 2018 at 15:44
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1\$\begingroup\$ Use a comparator on the front and it will take any regular waveform, you don't need to have a square wave input. \$\endgroup\$ Commented Sep 19, 2018 at 18:32
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\$\begingroup\$ The use of 555 for division in the question implies either fixed frequency or duty cycle irrelevance, since the duty stays constant. If applied to multiplication it makes the second part in this circuit completely redundant, as the same effect can be achieved with correct RC on gate alone \$\endgroup\$– MapleCommented Sep 19, 2018 at 20:05
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\$\begingroup\$ @Maple It's hard to get an accurate delay without trimming using the RC. Gates are too variable in threshold and hysteresis. The 555 is guaranteed to be within a few percent. So it's (perhaps) justified and it meets the stated requirement of using a 555. \$\endgroup\$ Commented Sep 19, 2018 at 20:07
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\$\begingroup\$ @JackCreasey True, provided the duty cycle isn't too short. The square wave input constraint gives the possibility of an approximately square wave output. \$\endgroup\$ Commented Sep 19, 2018 at 20:09
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A frequency multiplier is usually done with a PLL. A 555 chip is not typically a good starting point for designing a PLL.
PLL == Phase Locked Loop.
answered Sep 19, 2018 at 14:58
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\$\begingroup\$ Is it not possible with 555? Cannot actually use PLL that's why \$\endgroup\$– user172541Commented Sep 19, 2018 at 15:08
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\$\begingroup\$ It is possible to make a VCO using a 555 but the 555 isn't designed for that so it's cumbersome. A VCO is needed in a PLL. \$\endgroup\$ Commented Sep 19, 2018 at 15:58
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2\$\begingroup\$ @PMD: If there are constraints on your solution such as "cannot actually use PLL that's why" then these need to be stated and explained in your question not sprinkled through the comments. If you don't supply all the relevant information you'll wind up wasting a lot of people's time. Please edit your quesion to fix it. You might also edit to say whether or not you understand that your 555 circuit is not a frequency divider but a monostable as explained in the comments. \$\endgroup\$ Commented Sep 19, 2018 at 17:04
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\$\begingroup\$ @Transistor Will be careful next time... \$\endgroup\$– user172541Commented Sep 20, 2018 at 7:50