Electronics Lab Philippines

TIMERS

Offline bravokilo

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TIMERS
« on: March 06, 2019, 09:35:09 AM »
I wish to open this topic and did not find a more appropriate section. But since I will be discussing Flip flops, ok na siguru dito.


When we hear timer, what comes to our mind is the Hour glass. We see it as emptying the top or filing up the bottom. Let's think of the latter. The bottom is being filled up. The narrow neck  allow the fine sand to pass through slowly and uniformly. The amount of sand is calibrated top achieve the timer desired.

The above is purely mechanical. How do we do it electrically?

Ans. We fill up a capacitor.
l

To be continued.....   


 

Offline Super zHero

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Re: TIMERS
« Reply #1 on: March 06, 2019, 01:42:38 PM »
....will wait till we get to counters.

Offline marianoben

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Re: TIMERS
« Reply #2 on: March 06, 2019, 02:54:02 PM »
pa subs din po sir bk.

Offline bravokilo

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Re: TIMERS
« Reply #3 on: March 07, 2019, 06:41:46 PM »
Super , hinde ako marunong bumil;ang.hehe.

Welcome MarianoBen....

Well, you can do a simple experiment. Fill up a capacitor. How. Well, use 6 volts, get a 6-10 V electrolytic and charged it.

1. If you put the 6 volts, the charging is almost immediate.
2. If you series a resistor, it will take time.
3. If you series a POT, you vary the time to charge the capacitor.

But how do you detect if the CAP is fully charge?
You can use a tester to check the voltage.

How else?

Well, can an NPN transistor. Emitter to ground, collector to LED, LED to battery but a series resistor, try 1k so you won't the LED.

Now, get that POT say 10K and feed a forward bias to the tranny. As you increase the base V, the tranny will turn on and light up the LED. If too dim, lower the R to 500 ohms.

Now, you got it to light up. Ok, get the CAP and minus to Emitter, plus to Base. Short the lead to empty the CAP.(You can put a push button to discharge it everytime you need to).

Now, start the POT at the extreme end with the highest R.

The tranny will not come on until the CAP is charged up.

Turn the POT to lower the R. Soon the LED will light up.

There you are , you have a timer. You can change the time by moving the POT. Put a kob and a dial with paper underneath so you can mark the time to elapse on a particular setting of the POT.

Interesting, Nu?

Now, you might want to put a relay in place of the LED. Yep , get a 6 V relay but put a diode across its coil with the arrow pointing to the plus.

You see when the minus disappears when the tranny opens up, there will be
a a voltage kick from the coil of the relay and can destroy the tranny. The diode shorts it out.

The relay's contact can handle a different voltage/current(to turn on a motor or a bigger lamp.

You see, the CAP is like a water canister which has to be fill up first before it will discharge some water over the brim to wet the base.

So, ladies. what is an electronic timer? Ans: It is filling up a capacitor.

But, Oh, the 555 is a timer IC. Strictly speak , it is not. It only senses a capacitor filling up. It replaces the tranny. Pin 3 goes high when the cap  is filled up. But it has features like resetting. That is why it can be made to cycle up and become an oscillator.

It became the most popular IC like our Mega sardines "555". the inventor became rich but has since passed away already. He did not invent a timer IC.
It was a sensing IC.

Super, wait till I get to the 4060 IC. It is a more sophisticated timer IC.




You see, when the

 

Offline bravokilo

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Re: TIMERS
« Reply #4 on: March 07, 2019, 06:44:55 PM »



See this 555 IC, It has the R and the C. The R is the resistor controls the charging current to the C. I think Pin comes on when the C is 3/4 filled.

Offline bravokilo

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Re: TIMERS
« Reply #5 on: March 07, 2019, 06:47:05 PM »



Here is the 4060. Make your timer! 24 hour yan. You see C2 and the shorting button to reset. It is charging a capacitor!

Offline bravokilo

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Re: TIMERS
« Reply #6 on: March 07, 2019, 06:53:00 PM »



Counter IC. Look up 4017 too.

Super z, you can use this to count sheep till you fall asleep.

Look under RC in Mechatronics.....I will discuss the 4017. It is a Johnson counter and is widely used to make running lighs cuz it counts and cycles up and keep counting like crazy.

Offline Super zHero

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Re: TIMERS
« Reply #7 on: March 07, 2019, 08:44:26 PM »
I thought I've replaced the job of the 555 with a PIC micro for timing purposes.  But last year I came upon my reel of 1,000 pcs of TLC555 in SOIC-8.  So now what am I gonna do with them?

Offline bravokilo

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Re: TIMERS
« Reply #8 on: March 08, 2019, 10:07:15 AM »
AHA, PM YOUR PRICE PER PIECE. 

Offline bravokilo

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Re: TIMERS
« Reply #9 on: March 08, 2019, 10:12:47 AM »
oOPS...IN rEPLY 4, i DID NOT MENTION HE SIZE OF THE CAPACITOR. TRY 500 TO 1000 MFD. NOT TOO SMALL CUZ IT BE CHARGED IN TO TIME.

Offline bravokilo

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Re: TIMERS
« Reply #10 on: March 12, 2019, 05:55:49 PM »
Napunta tayo se everyday timers we can use like to keep light on  for the time chosen. Sa CR, sa Gate, etc...

Actually, I had wanted to discuss circuit analysis where we see a capacitor being charged.  It has sometime to do with delaying the ON or delaying the OFF of a tranny.  Assume the cap is zapped, it will be charged first before the tranny comes on. On the other hand, when the forward bias is removed, the tranny does not turn off instantly. The cap has to discharge first.

Of course we see CAPS in filters. We all built a power supply from an AC traffo. We put diodes but wqe will hear the hum or fluctuations in our audio amp-starvation. We put filter caps.

I started with tubes, so the electrolytics in the p[ower supply were critical. 40 MFD usually I remember. Then a choke is introduced and there is a cap before and after the choke, all to keep ripples and hums aaway.

In tansistors circuit, we see 1000 MFD or 2000 or even 20000 for our PS to power out transceivers before. Why higher for trannies. Cuz the voltage is low and the current is high. It is the other way around for tubes.

How does it filter the supply. Well, it charges caps. Look at them  as if they are rechargeable batteries with very short shelf charge. They getr filled up quickly when the load is low and when the load beomes suddenly high, the caps are energy reservoirs.

 

Offline bravokilo

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Re: TIMERS
« Reply #11 on: March 14, 2019, 01:57:50 PM »
     BACK TO A SIMPLE TIMER



     Press SI. The 100 µF electrolytic capacitor rapidly charges up at about 6 V. The transistor will be forward biased, and collector current will flow operating the relay. Release SI. The capacitor will begin to discharge via the 33 K resistor at the base of the transistor. When the voltage across the capacitor gets down to half a volt or so, the transistor base will no longer be forward biased, collector current will cease, and the relay will drop out. The capacitor will continue to discharge via the 47 K resistor

     With the values shown, the relay will remain operated for about eight seconds. Long times are possible with lower values of capacitance by substituting a Darlington pair for the 2N2926. In this case, increase the two resitor values into the megohm range.






Offline bravokilo

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Re: TIMERS
« Reply #12 on: March 14, 2019, 02:08:14 PM »
     This is as basic as it can be. A larger capacitor will take longer to dischar of course.

     We can mod this circuit the way I discussed previously. Replace S1 with a variable resistor.

     Remove the 47K and replace it with a push button switch to ZAP the capacitor.

     Maybe put a switch between the Emitter and battery.


     Zap the cap,set the variable resistor (POT), switch ON. The CAP will
take time to charge then turns the tranny and relay ON.

     To increase the time to charge, insert a resistor in series to the POT.


Offline bravokilo

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Re: TIMERS
« Reply #13 on: March 14, 2019, 02:10:19 PM »


Offline bravokilo

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Re: TIMERS
« Reply #14 on: March 14, 2019, 02:21:14 PM »
This is circuit for aa servo amplifier using discrete components....

Se the lower circuit where you find the 1.5K POT. Note C1, R1, and VT1. RI and C1 forms a timer to turn on VT1. EVrytime VT2 comes on, it send a minus to C1 via D1. It zaps mC1. But C1 begins to recharge and at a certain point, it will turn VT1 On and turns VT2 OFF. VT2 creates the local negative pulse sent to the junction via R8. The POT influences the time C1 gets recharged! So, the POT sets the pulse width.

Take note, R1 is fixed to recharge C1. It is the other side of the CAP that is conneced to the POT via R4.

If you have a scope you can observe the local negative pulse in in R8. If you increase the value of C1, you will see a wider width in the pulse.

Re: TIMERS
« Reply #15 on: April 06, 2020, 04:20:57 PM »
Super , hinde ako marunong bumil;ang.hehe.

Welcome MarianoBen....

Well, you can do a simple experiment. Fill up a capacitor. How. Well, use 6 volts, get a 6-10 V electrolytic and charged it.

1. If you put the 6 volts, the charging is almost immediate.
2. If you series a resistor, it will take time.
3. If you series a POT, you vary the time to charge the capacitor.

But how do you detect if the CAP is fully charge?
You can use a tester to check the voltage.

How else?

Well, can an NPN transistor. Emitter to ground, collector to LED, LED to battery but a series resistor, try 1k so you won't the LED.

Now, get that POT say 10K and feed a forward bias to the tranny. As you increase the base V, the tranny will turn on and light up the LED. If too dim, lower the R to 500 ohms.

Now, you got it to light up. Ok, get the CAP and minus to Emitter, plus to Base. Short the lead to empty the CAP.(You can put a push button to discharge it everytime you need to).

Now, start the POT at the extreme end with the highest R.

The tranny will not come on until the CAP is charged up.

Turn the POT to lower the R. Soon the LED will light up.

There you are , you have a timer. You can change the time by moving the POT. Put a kob and a dial with paper underneath so you can mark the time to elapse on a particular setting of the POT.

Interesting, Nu?

Now, you might want to put a relay in place of the LED. Yep , get a 6 V relay but put a diode across its coil with the arrow pointing to the plus.

You see when the minus disappears when the tranny opens up, there will be
a a voltage kick from the coil of the relay and can destroy the tranny. The diode shorts it out.

The relay's contact can handle a different voltage/current(to turn on a motor or a bigger lamp.

You see, the CAP is like a water canister which has to be fill up first before it will discharge some water over the brim to wet the base.

So, ladies. what is an electronic timer? Ans: It is filling up a capacitor.

But, Oh, the 555 is a timer IC. Strictly speak , it is not. It only senses a capacitor filling up. It replaces the tranny. Pin 3 goes high when the cap  is filled up. But it has features like resetting. That is why it can be made to cycle up and become an oscillator.

It became the most popular IC like our Mega sardines "555". the inventor became rich but has since passed away already. He did not invent a timer IC.
It was a sensing IC.

Super, wait till I get to the 4060 IC. It is a more sophisticated timer IC.




You see, when the


Im new here and really not that techy or something but this is really cool

Offline >>>^żżż^<<<

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Re: TIMERS
« Reply #16 on: April 13, 2020, 10:52:33 AM »
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