TL494 – which component works with lower frequencies?

Hello All,
I have been asked by a friend to find for him (he´s very busy in the moment) a component, that
- works (other than TL494) also with very low frequencies (till 1 to 10 Hertz range)
- can create 2 phase-shifted square-wave-signals with time delay.
Hope, you can help. Thanks

Hi Gunther


The TL494 operates roughly 300Khz to 500khz if you need to progress to the level of 10 hertz and below I would suggest using pic micro or Atmel and write the software yourself using adc conversion to monitor the output voltage / current but If you are going to do this ….. Don’t forget to put a test routine into your software so that in the event of fault symptoms you avoid the chicken or the egg story such that you cannot isolate the fault

"Classic example is a recent design I’ve worked on some years ago featuring the new Class G Amplifier in which the incredible designer decided not to incorporate a test routine or sub procedure

This cost the customer £500 a peace with a refusal from the designer to modify the design and cost the company god knows how much money including people jobs and mine because he simply wouldn’t listen or acknowledge that his design was in fact destructible and like all good things always will always develop a fault at some stage no matter how brilliant you are "

So if you are going this route , fine but make sure you put a test procedure into your IC before you market the final design so as to make the design viable otherwise your going to have some very angry people on your doorstep whishing to sue you for everything you own “Word warning!!” take heed of my advice unlike the other people who decided they didn’t need to listen to me at all

I can think of at least 3 or 4 major pls who fell into this trap Im quite sure there will be a few more yet

No one is that clever that they don’t need to listen to what other people have to say no matter how small they are or how big they think they are

Gunther, the waveforms you have show something a bit different that two phase shifted squarewaves. It appears that you want two squarewaves with some dead time. To generate this type of waveform I have used the 4017 along with diode ORing.

Hi Mark,

thank you for your suggestion. Right now I think of using Analog Devices, which is open source, programable and has standard PWM and works on 78 Hertz (without dead time). But that´s only the workaround, if I don´t find a simplier solution. But I agree, the TL494 is not the best piece that Texas Instruments has built so far

Thanks David,

you are right. Will check out your suggestion. Is the 4017 suitable for low frequencies?

Yes the 4017 will work from DC to about 1 MHz. It is a decade counter that may or may not suit your purpose. Here is how to configure it to produce a 10 Hz squarewave having a duty cycle of 40%. Drive the CLK input with a 100 Hz clock. Connect outputs 0, 1, 2, and 3 to a 4 input OR gate or diode OR it.

David, that sounds great. Will check it out. Thanks!

Hi Gunther


There is also another way of achieving this with D type flip flops and a 555 pwm circuit Im attaching a link for you to see

http://www.sentex.ca/~mec1995/circ/pwm555.html

Hope this helps

Mark

Hu Gunther here is another circuit that I think you might find interesting as well
http://www.bowdenshobbycircuits.info/boost.htm

Mark

www.harrington.force9.co.uk

Hi Mark,

thank you for your suggestions. Can the dead times be adjusted by adjusting the pulse width?

I just heard from an expert, that the 4017 is - as he called it - a Methuselah, which has difficulties in adjusting the phase exactly. Is this also your experience?

Is there any other component you can think off, that could do the job?