# Frequency of signals

Discussion in 'The Projects Forum' started by Cerkit, Feb 2, 2009.

1. ### Cerkit Thread Starter Senior Member

Jan 4, 2009
286
3
Hi. I need to find a way to generate signals of different frequencies using the same circuit so that I can swap through them. Have considered using oscillator but can not find one with good range and plus the very good ones are only useful for a small variation in frequency. Need to swap through frequencies between range of 17000Hz and 50000Hz.

2. ### SgtWookie Expert

Jul 17, 2007
22,201
1,809
Are you looking to generate square waves, pulses, triangle waves, sine waves?

For square waves and pulses, you could use a 555 timer with a few extra components.

For triangle waves or sine waves, things get a bit more complicated.

3. ### Cerkit Thread Starter Senior Member

Jan 4, 2009
286
3
Well square wave would be more desirable but I have been told I won't be able to get very good precision with the 555. I need at least 4 digit precision hopefully 5.

4. ### eblc1388 AAC Fanatic!

Nov 28, 2008
1,543
104
With precision down to 5 places, that's down to Hz for 50,000Hz. Only a DDS generator can fulfill your needs.

You can look up Google for "DDS frequency generator".

5. ### Cerkit Thread Starter Senior Member

Jan 4, 2009
286
3
How precise could the 555 be?

6. ### Cerkit Thread Starter Senior Member

Jan 4, 2009
286
3
DDS to complicated/expensive for the application required need simple and compact

7. ### eblc1388 AAC Fanatic!

Nov 28, 2008
1,543
104
Your requirement is not specific enough. Can you give some examples of what is required?

1. Do you want just several fixed frequencies inside the range of 20,000 to 50,000Hz or they are continuously variable?

2. Do the frequencies needed be specific and spot on every time? e.g. 24,567Hz every time or anything from 24,560 to 24,570Hz be OK?

3. Making your goal too ambitious just complicate the ultimate circuit design.

8. ### SgtWookie Expert

Jul 17, 2007
22,201
1,809
If you need 4 or 5 digit precision in that frequency range, then you need a crystal oscillator. You could build something in the MHz range, and divide it down using a microcontroller or other circuitry.

9. ### Cerkit Thread Starter Senior Member

Jan 4, 2009
286
3
What other circuitry can I use to divide the frquency?