Timeline for Why are two 555 timers in separate sub-circuits cross-talking? (Poltergeist in the Breadboard)
Current License: CC BY-SA 4.0
9 events
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| Jan 25, 2021 at 19:27 | comment | added | Voltage Spike♦ | No, it's probably not possible to be a working EE these days without knowing and working with TTL. However, I stopped prototyping with breadboards shortly after my first job, I found they weren't that useful, probably because I do mixed designs and not strictly digital. If I do prototype I solder, its not that much harder and no worry about cross capacitance. | |
| Jan 22, 2021 at 7:28 | comment | added | Uwe | So you got no personal experience with digital TTL and 555 circuits at all? | |
| Jan 22, 2021 at 0:13 | comment | added | Voltage Spike♦ | I have also seen videos of people having issues with TTL schmidt triggers they ended up throwing away their breadboards | |
| Jan 22, 2021 at 0:07 | comment | added | Uwe | This is about a very simple timing circuit using a 555. Your sophisticated designs may have problems with parasitics, but not this very basic circuit from a book for beginners. I worked with TTL circuits up to 10 MHz with sucess using simple prototypes. (40 years experience) Bypassing was important, but not inductive parasitics. Digital designs, the circuit of the question is digital too. | |
| Jan 21, 2021 at 23:44 | comment | added | Voltage Spike♦ | Not so, my designs work at 5Hz and parasitics are very important. None of my designs would work on a breadboard | |
| Jan 21, 2021 at 23:43 | comment | added | Uwe | The question is about a very low frequency circuit flashing two LEDs. Frequency about 1 to 5 Hz, maximum about 15 to 20 Hz. So inductive and capacitive parasitics are no problem. Only a bypass capacitor is needed for the 555 chips. Soldering prototypes may be important at much higher frequencies in the kHz and MHz range. | |
| Jan 21, 2021 at 16:26 | comment | added | Voltage Spike♦ | Even with capacitors breadboards have enough parasitics (inductive capacitive and resistive) that coupled with wires can have issues with strain relief and connection. This gives breadboards the opportunity for many poltergeists. I thought I would point those out, because breadboards are not great tools for prototyping. And yes, the breadboard is at fault, because the inductance of conductors creates the need for bypass capacitors in the first place. Most good analog designers use soldering as a primary prototyping method. | |
| Jan 21, 2021 at 9:07 | comment | added | Uwe | The poltergeist is not the breadboard, it is the misuse of the breadboard by not using capacitors for supply voltage close to the IC. If used with capacitors, circuits on breadboards work well. | |
| Jan 20, 2021 at 20:46 | history | answered | Voltage Spike♦ | CC BY-SA 4.0 |