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| Portable Low Frequency square wave generator circuit - Solved - page 3 |
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| 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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