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How to make a oscillator?

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tussi

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How can I make a 3v oscillator with some cheap components?? I need it for a remote control. The frequency must be between 1k and 10kHz.

Please help me
 
How can I make a 3v oscillator with some cheap components?

It doesn't get any better than this. The frequency stability is pretty good, the parts aren't hard to come by, and it will work on 3.0V.

The collector resistor values aren't too important, just make them one-tenth the size of the base timing resistors for a reasonably good square wave, and select the base resistors so that the transistors go into saturation ( V(CE)= 0.2V nominal ). Select the timing capacitors for the desired frequency.

NBD
 

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Hi thanks for replying :D
Is there a way i can use an opamp to solve this?? I want to use it in a ir remote control, so it need to be small. If I can use an opamp it would be the cheapes because i allready have a lot of them 8) .
 
Hi will this work in "real life" ?? It worked in pc simulation but....
 

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Miles, why did you include 2 ln(2) in the equation?

Shouldn't it just be 1/(2RC) for the frequency.

and if you just wanted to know the delay, dont even add the 1/ in the equation.

The astable is what I use the most for low frequency applications. In fact, it fits on a 2cm by 2cm square board.
 
Hi thanks for replying :D
So I can use this??
I just need to generate a freqency so I can remote control an mcu. I want to wake it and sending it to sleep using IR..
by the way, sorry for my realy bad english :cry:
 
Most opamps won't work off 3V, the very simple (and cheap) multivibrator design posted above will happily work off 3V.

In fact, it will work off 1.5V - I built a signal injector probe back in 1971 that used a multivibrator and a single AAA battery. I used it at work for doing audio and radio repairs, the harmonics from the squarewave output easily work at AM IF frequencies, and even medium wave RF frequencies.
 
Miles, why did you include 2 ln(2) in the equation?

Shouldn't it just be 1/(2RC) for the frequency.


The astable circuit given in a previous post operates as follows.

When Q(1) goes into saturation, it connects the positively charged plate(s) of Q(2)'s timing capacitor to ground. If you ground the positive side of a capacitor, the opposite plate(s) must become negative with respect to ground. That negative voltage turns Q(2) off. This allows Q(1)'s timing capacitor to charge to V(cc) through R(c), ready for the next half-cycle. This occurs as the negative voltage at the base of Q(2) charges towards V(cc) through the base resistor. Once this voltage reaches ~0.6 V, Q(2) turns on, saturates, and forces Q(1) off. Each transistor therefore completes one cycle: t= t(1) + t(2). That would account for the factor of "2" in the frequency calculation.

Now take a LQQK at the enclosed diagram. This gives the situation which occurs as you charge a capacitor through a resistor. If you consider a capacitor charging to: V(c)= 0.5V(DC), and solve the equation for t, you will see that this becomes: t= RCln(2). If you drop the ln(2) term, then you will get:

V(c)= 0.6321V(DC), which is greater than 0.5V(DC). It will never arrive at that value, since the transistor will already have turned on.

Where: ln(2) is the "natural" (so called since these logarithms "naturally" give the easiest solutions to differential equations) log of 2. ln(2)= 0.693147180560 (approx). That's where 2ln(2) comes from.
 

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that is the 1st time I've seen that approach.

1 / (2 * C * R * 0.69)

I'll keep it simple for ya.
 
Try my CPO it works on as low as 1.5vdc
 

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I think Miles's design is still better. I have tried a circuit similar to the last design, and found out that even though the volume as louder, the transistors were heating up like crazy, especially when they were rated at 500ma.
 
mstechca said:
I think Miles's design is still better. I have tried a circuit similar to the last design, and found out that even though the volume as louder, the transistors were heating up like crazy, especially when they were rated at 500ma.

The last circuit posted will get hot, for a couple of reasons:

1) It's directly driving an 8 ohm speaker.

2) It's been pruned of components too much, there's nothing to restrict current flow at all.

The circuit itself is just a variation of the multivibrator posted earlier, by using NPN and PNP transistors you can simplify it considerably.
 
I usually use a TO3 Transistor with a heatsink for the PNP

This is the circuit we made in high school electronics class 30 years ago
 
I always ignore transformer and inductive coupling because:
a) Transformers cost alot of money
b) Transformers are too big
c) The signal might not pass through if the primary and secondary are far apart especially at microwave frequencies.
d) I have to worry about the inductance on two sides.

I ignore direct coupling because:

a) It wastes power
b) huge transistors may be required
c) The second stage can hog the DC power from the first stage, making direct coupling almost useless.

So that leaves me with capacitor coupling. Even though it places a frequency limit, I STILL USE IT because:

a) one stage wont hog DC power from another one because of a capacitor.
b) The current can be set by the resistor connected between battery and the coupling capacitor
c) results are generally better.

now thats why I use the 1st circuit instead of the 2nd.
 
mstechca said:
I always ignore transformer and inductive coupling because:
a) Transformers cost alot of money
b) Transformers are too big
c) The signal might not pass through if the primary and secondary are far apart especially at microwave frequencies.
d) I have to worry about the inductance on two sides.

You seem to be worrying without much justification?. However, transformer are generally things to avoid (unless required), for reasons a) and b) (c and d don't make much sense?), but more importantly they are often difficult to obtain.

I ignore direct coupling because:

a) It wastes power
b) huge transistors may be required
c) The second stage can hog the DC power from the first stage, making direct coupling almost useless.

None of those make much sense, none apply to a correctly designed circuit. Even the simple oscillator above isn't crude for lack of capacitors, it's crude for lack of resistors.

So that leaves me with capacitor coupling. Even though it places a frequency limit, I STILL USE IT because:

What frequency limit?.

a) one stage wont hog DC power from another one because of a capacitor.
b) The current can be set by the resistor connected between battery and the coupling capacitor
c) results are generally better.

Again, none of these make much sense, or have any relevence.
 
mstechca said:
I ignore direct coupling because:

a) It wastes power
b) huge transistors may be required
c) The second stage can hog the DC power from the first stage, making direct coupling almost useless.
All opamps and most audio power amps are direct coupled and have none of the problems you have.

The very simple oscillator that gets hot because it is missing resistors is part of the design of the LM3909 IC which doesn't get hot and even has a voltage-doubler inside. It is also direct coupled. :lol:
 
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