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Electronics => Beginners => Topic started by: wolfrum on June 27, 2011, 07:37:25 pm

Title: 555 TIMER current and voltage
Post by: wolfrum on June 27, 2011, 07:37:25 pm
i need to draw 0.6A and 15v from a 555 timer ,i was able to get only 6v then 555 starts giving continuous signal.I used opamp to amplify but my load required 0.6A so the opamp could not amplify please suggest a circuit .i would greatly be helpful
Title: Re: 555 TIMER current and voltage
Post by: Psi on June 27, 2011, 08:10:28 pm
If you just want to turn something on/off and don't need a push/pull output you could use a NPN transistor.
The 5V 555 output could go through a ~680R resistor to the base of the transistor. Emitter would go to ground and the collector would go to the negative side of your load. The positive side of your load would then go to + 15V.

Or, if you do need push/pull output you could use a high power opamp.
You can get them with high powered drivers built in.
Title: Re: 555 TIMER current and voltage
Post by: Zero999 on June 27, 2011, 08:12:00 pm
It's very important to read the datasheet for the components in your design before using them.

Look at the 555 datasheet (try Google) and it will become obvious why it smoked when you tried to draw 600mA from it. Using a standard op-amp will not help because it's output current is probably less than the 555's, again read the datasheet.

The solution is to use a transistor to switch the desired load. I found the following circuit using Google.
(http://www.electronics-tutorials.ws/waveforms/tim46.gif)
(http://www.kpsec.freeuk.com/images/tranload.gif)
http://www.google.co.uk/search?client=opera&rls=en&q=555+treansistor&sourceid=opera&ie=utf-8&oe=utf-8&channel=suggest#sclient=psy&hl=en&client=opera&rls=en&channel=suggest&source=hp&q=555+transistor&aq=f&aqi=&aql=&oq=555+transistor&pbx=1&bav=on.2,or.r_gc.r_pw.&fp=ff8427f75c87ad4&biw=1920&bih=921

Reading the tutorial where I got it from would also probably help you.
http://www.electronics-tutorials.ws/waveforms/555_timer.html
http://www.google.co.uk/url?sa=t&source=web&cd=1&ved=0CCIQFjAA&url=http%3A%2F%2Fwww.kpsec.freeuk.com%2Ftrancirc.htm&ei=XQkKTvvgAtCwhAeMnojpDw&usg=AFQjCNFYhE8edWq5EddzHubCsMNyiy92BQ

Again, read the datasheet before using the transistor.
Title: Re: 555 TIMER current and voltage
Post by: ivan747 on June 28, 2011, 03:38:46 pm
i need to draw 0.6A and 15v from a 555 timer ,i was able to get only 6v then 555 starts giving continuous signal.I used opamp to amplify but my load required 0.6A so the opamp could not amplify please suggest a circuit .i would greatly be helpful

Why are you asking in this section?
Moved
Title: Re: 555 TIMER current and voltage
Post by: Lawsen on June 28, 2011, 07:25:24 pm
I agree, that this post is in the wrong place, because the subject is not a general chat.  It needs to be at the Projects, Designs, and Technical Stuff.  The general section is for how is the weather at your place, austerity and unemployment rates causing you to suffer or have less things in life, or are the birds chirping at your outside tree bothering you. 

The 555 multivibrator oscillator transistor-transistor logic IC is not made to operate in 15 V DC.  It cannot give such a high volts peak in the square wave.  Op Amps are not meant for such a high volts peak, either.  You will need a continuous load, of the amplifier can be ruined.  I almost want to suggest a power amplifier, but I have no experience with this.  An opto-relay might with used to switch on and off the 15 V from a 15 V DC power supply output.  The opto-relay is fast and silent and can take the 5 V square wave signal from the 555 oscillator and switch the output of the 15 V DC power supply that is left continuously on.  The 15 V DC output signal needs to be conditioned with a bounce less circuit or capacitor in Don Lancaster TTLogic Cookbook. 

There are two ideas, switching the output of 15V DC power supply or input to a power amplifier.  Power amplifier requires a continuous load and specific impedance - resistance, otherwise the amplifier will be ruined, blown amp.  Why do you have to build this invention? 

Lawsen
Title: Re: 555 TIMER current and voltage
Post by: Zero999 on June 29, 2011, 04:42:11 pm
The 555 multivibrator oscillator transistor-transistor logic IC is not made to operate in 15 V DC.
The 555 timer's absolute maximum rating is 16V so running it off 15V should be no problem.

Quote
I almost want to suggest a power amplifier, but I have no experience with this.
The only power amplifier you need is a single transistor or MOSFET.

Quote
An opto-relay might with used to switch on and off the 15 V from a 15 V DC power supply output.  The opto-relay is fast and silent and can take the 5 V square wave signal from the 555 oscillator and switch the output of the 15 V DC power supply that is left continuously on.
An relay is only required when you need isolation, for example, the load is connected to the mains, otherwise a transistor is all that's required. If the load requires the positive to be switched rather than the negative, two transistors can be used: PNP and an NPN transistor.

(http://www.winpicprog.co.uk/graphics/lamp_source2.gif)

I repeat, there is no need to run the 555 timer from a 5V regulator, 15V will do and the CMOS 7555 will work fine up to 18V.

Quote
The 15 V DC output signal needs to be conditioned with a bounce less circuit or capacitor in Don Lancaster TTLogic Cookbook. 
There should be no need for any de-bouncing. Providing the 555's power supply is well decoupled and there's a 10nF capacitor between pin 5 and 0V, the output waveform should be clean and glitch free.