Tutorial: 555 astable timer resistor and capacitor calculations | EDUQAS GCSE Electronics
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- Опубліковано 9 січ 2020
- Step-by-step video for my students. I show you how to calculate component values by re-arranging the astable timer formula. This is ESSENTIAL viewing if you are not confident re-arranging the formula and/or using a scientific calculator. In this video I use my Casio fx-991EX.
thank for your reply
Hello, R3 would be same as R1?
The resistor indicated as R3 is a current-limiting resistor for the LED. It's value depends on the supply voltage (Vs), forward voltage drop (Vf) and forward current (If) of the LED. None of these parameters are related to the timing components R1, R2 and C. If you want a reasonably balanced duty cycle (on / off time approximating to be equal, but never exactly so) R1 should be much less than R2, with R1 generally being no less than 1K.
I’m trying to make a controller for a dc motor from my research I have done online 50hz -100hz is best for a brushed dc motor. With that being said I did my calculations for 60hz R1 1k R2 76k C20mf is this correct will it work? I’m also curious how do I connect a e-bike twist grip throttle to control the motor speed. I want to put 555 timer to mosfet Sorry if these are dumb questions. I’m just starting to learn this stuff
50 - 100Hz PWM would be very slow. I recall that PWM motor controllers are typically 2kHz or greater, but I'm not aware of a calculation to find the optimal frequency. Don't forget that PWM uses a fixed frequency, and the speed control is achieved by varying the duty cycle. I have no experience of twist grip throttles.
@@PizzeyTechnology thanks for the reply
I need it to be on for an hour and off for an hour and the calculations I made are: r1 10k r2 340k c 15000uf, is that correct?
You've done the calculations correctly but you may find performance is not as expected. The charging current for the capacitor would be very small and the capacitor leakage current could therefore be a problem - it might never charge to the 2/3 threshold. Component tolerances might also be a problem but that depends on how accurate you want the timing to be. If you want to implement long delays a microcontroller-based circuit might be a better solution.
How can I use a clock alarm to activate a relay?
@@agus-lq8vv Depends on many things. What signal does the alarm clock produce? What relay do you hope to use? Will the relay latch on? etc.
The clock is similar to the one seen here ua-cam.com/video/L2dwC3BsvQc/v-deo.html I want to use the speaker signal to activate a relay as seen here ua-cam.com/video/V0-X_Ton84Y/v-deo.html and I need to know what circuit to use. All this is for a school automation project. Sorry if I do not understand much is that I am from Argentina and I am using google traslate jaja
How to calculate if use just one resistor and one capacitor?
If you have only a single resistor then it won't be an astable. Beware of omitting the top resistor as pin 7 (discharge) is an open collector.
@@PizzeyTechnology is it can if use 1resistor 1capcitor to make led blinking?
It would help if you could define the problem further (it's not a school homework is it?). Does the circuit have to use a 555 timer or could it use some other component?
It's actually quite easy to build a 555 astable circuit using just one RC timing network (one resistor and capacitor), but it's operation is different to the one I posted about previously.
@@PizzeyTechnology Which condition that make battery fast weak n drain?...using capacitor 10uf or 100uf?.
Fast blinking rate or slow light will weak the battery?