Electronics > Beginners
Portable Low Frequency square wave generator circuit - Solved - page 3
soldar:
I remember building decades ago a pulse generator which could go from (say) 1% to 99% duty cycle and voltage from something like 5 V to about 15 V. It was for lab testing some devices and it was simply a 555 with a variable voltage supply and the supply was little more than a pot voltage divider with an emitter follower transistor. Put it all in a nice box and it felt like it was something. I was working for Kodak at the time and my co-workers looked up to me like I was a genius.
But, yes, the 555 timer is not a precision thing. Changing one thing , like supply voltage, will affect the others. It is good for simple, quick and dirty solutions.
Zero999:
I wonder if the first 7555 was faulty, or is that kind of error normal? I just don't have the time or motivation to test a whole load of ICs.
nsrmagazin:
Here is the power supply:
http://powersupply33.com/simple-split-rail-power-supply-lm380.html/split-power-supply
For "Vin" you have 2x"9VDC" batteries in series.
Here is the circuit itself for what you need.
http://hyperphysics.phy-astr.gsu.edu/hbase/Electronic/square.html
Making the resistor a pot gives you varying frequency.
The tolerance will depend on the components used. Recommended are "1%" tolerance resistors.
spec:
--- Quote from: soldar on January 31, 2019, 03:46:55 pm ---I would appreciate a little more politeness and less rudeness. I make a habit of trying to ignore rudeness because I prefer not to escalate.
--- End quote ---
In that case, you should practice what you preach. And you did escalate.
spec:
--- Quote from: soldar on January 31, 2019, 03:46:55 pm ---
I have been working with 555 timers since before most people on this forum were born. In 1977 I was already using 555 timers and bought The IC Timer Cookbook (pdf) which I still have on my shelf. Around 1980 I was running a small home business with a friend building and selling timers for photography enlargers. A lot of people were developing their own photos at home and needed a timer for the enlarger. We sold maybe a thousand or two. I still have the circuit and PCB. Two scales: up to 60 seconds and up to 3 minutes.
The LM555 (pdf) is bipolar and the mother of all later CMOS
--- End quote ---
It doesn't matter what you have done or what you are. That does not grant you the right to make derogatory unfounded statements about other peoples designs.
Just for the record, I have been designing circuits since before the 555 was even thought of. In fact I had a 555 chip before they were released in the UK.
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