Moderators: Dave Moll, Andrew Davie, Steve Anderson
Steve Anderson wrote:When you do get the correct chips, don't plug them in all at once, start at the beginning, sort out the oscillator, then move on to the downstream stuff. Slowly, slowly, catchee monkey.
Steve A.
ppppenguin wrote:The oscillator in any 4046 or HC4046 is NOT a precision device. You certainly don't want to rely on it being stable outside a phase locked loop. It will drift sginificantly with time and temperature.
At 3MHz it should be fairly predictable but there will be signficant differences between different manufacturers and even between different parts from the same maker. For a 1 off amateur project it doesn't matter if you have to AOT component values.
Steve Anderson wrote:Wow! What's going on here? As ppppenquin mentioned these oscillators are not precision devices, I did say you'd probably have to fiddle around with some of the component values.
But whatever is currently coming out of the 4046 make a note of it in frequency terms. Then go down the 'ladder' of outputs on the 4040 and each should be half of the previous. I have double-checked I got the correct pins on the 4040 against the Philips datasheet.
If they aren't my next move would be to fire up one of your 'real' oscilloscopes, OK they don't have a frequency readout but they should easily cover up to 10MHz. Measure the period (rising edge-to-rising edge) in us/ns of the waveform at the 4040 pin 10. First, is it stable? If yes then go down the 'ladder' of the 4040 and ensure that each output is twice the time (half the frequency) of the previous...ensuring they are rock-solid stable too, and a 50% duty-cycle, equal high and low time.
Without a specification for the little LCD scope I'm wondering if it can cope with these frequencies, it may only be good to upper audio frequencies even though it may display the waveform correctly(?).
Steve A.
ppppenguin wrote:A scope is essential for anything beyond the most basic design work. Obviously not everyone needs an all singing all dancing instrument but a simple dual trace 20MHz analogue scope can do a lot of work. In the UK there's a good choice of secondhand instruments for under £50. Hameg scopes are solid and reliable in that price range. Probably more so than Tektronix. Digital scopes have improved a lot. I have a Rigol DS1054 which was about £250 new and it will do everything you could possibly want for SD and NB TV. I still love my pure analogue 400MHz Tek 2465B - you'd have to prise it out of my cold, dead hands. But that's way more than you'd need here.
[/quote]Steve Anderson wrote:The last couple of stages (6.6 & 13.2kHz) seem plausible, but above that it seems almost random. I still strongly suggest getting a 'real' scope on this first, we'll attack the actual frequencies later.
Yes i was studying the doubling halving it does go strange ,i will get it out on the old scope and look ..I had a look at the ebay pages, there's no mention anywhere of its performance or limits. It appears to be a transistor tester first and the frequency meter/scope is a bolt-on goodie. After all they illustrate it showing 5000Hz, not in the 100s of kHz or MHz.
Steve A.
ppppenguin wrote:The ABC/123 pin equivalents looks fine to me.
Another data sheet: https://assets.nexperia.com/documents/d ... CT4040.pdf
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