Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

555 timer noise reduction

Status
Not open for further replies.

unlv007

New Member
Hello
I am made a simple 555 timer producing 10V pulses as per the website
**broken link removed**
The circuit diagram from this website is attached below.
I need pulses from 25V to 35V. Therefore i connected a 25V DC supply in series with 10V 555 timer output.

While testing the circuit, i found two problems.
1) At the instant the pulse transition occurs from high to low or vice versa, the power supply for driving the 555 timer also fluctuates. How to avoid this problem? Why does it occur?
2) The transition is more like a ramp from 25V to 28V and then to 35V. How to make it abrupt transition?
Thanks
 

Attachments

  • LM555Astable.gif
    LM555Astable.gif
    7 KB · Views: 821
That sounds like a pretty good way of destroying a 555 timer.

I'm not meaning to be rude but what is the point of this?

What exactly are you trying to do?

This isn't one of the things that you would normally do in isolation; it is typically part of a larger project. It is easier for us to provide help if we can see the bigger picture.

It sounds like you need to add a transistor to the output to drive the load but it depends on if it matters whether the pulaes are positive or negative.
 
I use these pulses to trigger a chemical reaction. For all electronics purposes, the reaction product can be considered to be a resistor whose value increases with time non linearly. I need to produce a 25V- 35V type pulses due to which i used the 555 timer.
 
Hi unlv007,

why don't you leave the regulator circuit for the timer just to the timer? Switching a load with the timer circuit connected to the timer's power supply will cause fluctuations.

Use two different power regulators: +10V (LM7810) for the timer circuit and an LM317T to adjust from 25 to 35V.

I also recommend using two separate rectifier circuits. The LM7810 can only have a max. input voltage of 25V.

Boncuk
 
Use two different power regulators: +10V (LM7810) for the timer circuit and an LM317T to adjust from 25 to 35V.

I also recommend using two separate rectifier circuits. The LM7810 can only have a max. input voltage of 25V.

Boncuk

thanks for your feedback.
What type of rectifiers - i know full wave/ bridge wave etc, or should i connect an RC filter to protect against fluctuations?
Can i use LM317 for my 10V timer supply as well as 25V DC supply?
 
Hi unlv007,

fluctuations are caused by load changes. In your particular case switching 25 to 35V out to the electrolytic device will cause them by increased current flow.

Additionally the circuit layout might have some influence, too.

You can use the LM317 to adjust the voltage between 25 and 35V. If you want to use it as well for 10V power supply for the timer circuit the problem will persist.

Hopefully an LM7810 is not beyond your budget. It costs the fortune of 50Cents. ;)

For good results a bridge rectifier is certainly the best choice.

Boncuk
 
Last edited:
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top