Timeline for Astable 555 circuit always on, not oscillating
Current License: CC BY-SA 4.0
19 events
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| Feb 22, 2022 at 20:19 | history | edited | hacktastical | CC BY-SA 4.0 |
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| Nov 4, 2021 at 19:55 | history | edited | hacktastical | CC BY-SA 4.0 |
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| Jun 23, 2021 at 19:44 | comment | added | Mike Felts | Hadn't thought of that! I'll take a look tonight. | |
| Jun 23, 2021 at 19:43 | comment | added | hacktastical | You can probe the pins of the chip itself to see what's going on. | |
| Jun 23, 2021 at 19:43 | comment | added | Mike Felts | Pin 4/Reset is tied to VCC/+. | |
| Jun 23, 2021 at 19:41 | comment | added | Mike Felts | What would checking ground and power look like? Its successfully powering another LED on the breadboard that I have setup as basically a canary. My multimeter probes are too large for the breadboard so have some alligator clip jumpers on the way, so if its just checking to make sure power is +5V, etc, then I should be able to do that in a day or two. Thanks for the schematic of the 555. One thing I did like in Ben Eater's video is that he shows how the chip works, including a chart of voltage in the cap over time vs output from the chip over time. I know its a simple chip, but seems cool! | |
| Jun 23, 2021 at 19:40 | comment | added | hacktastical | Is pin 4 (RESETn) tied to VCC? If RESETn is low, the output will be high. | |
| Jun 23, 2021 at 19:39 | history | edited | hacktastical | CC BY-SA 4.0 |
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| Jun 23, 2021 at 19:38 | comment | added | Mike Felts | Thanks for the options hacktastical! I tried spreading the 1M resistor across the chip so it reached discharge (thankfully I hadn't trimmed the wires yet) and it didn't change anything; the LED is still constantly on. | |
| Jun 23, 2021 at 19:25 | history | edited | hacktastical | CC BY-SA 4.0 |
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| Jun 23, 2021 at 14:58 | comment | added | hacktastical | One thing you can try is to connect the 1M to output instead of discharge. This also functions as an astable. Other than that, check ground, power, etc. 1uF and 1M are acceptable values for the 555. | |
| Jun 23, 2021 at 11:39 | comment | added | Mike Felts | I have a .1uF cap on CV (C2, the one I marked as 10 mF by mistake) and also have a .01uF cap across positive and negative (not shown in the schematic because I couldn't figure out how to draw it). | |
| Jun 23, 2021 at 11:37 | comment | added | Mike Felts | The schematic he shows is for the final form. I think the only thing I've switched out is the variable pot (I'm going based on an intermediate part of his 1st video) as I wanted to make sure that wasn't the issue. I've tried it with the variable pot in place as well (with the 1k resistor inline) and it didn't make a difference, so wanted to remove variables to troubleshoot as it -should- be oscillating without the variable pot in place of R2. | |
| Jun 23, 2021 at 3:49 | history | edited | hacktastical | CC BY-SA 4.0 |
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| Jun 23, 2021 at 3:23 | history | edited | hacktastical | CC BY-SA 4.0 |
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| Jun 23, 2021 at 1:23 | history | edited | hacktastical | CC BY-SA 4.0 |
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| Jun 23, 2021 at 0:57 | history | edited | hacktastical | CC BY-SA 4.0 |
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| Jun 23, 2021 at 0:51 | history | edited | hacktastical | CC BY-SA 4.0 |
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| Jun 23, 2021 at 0:43 | history | answered | hacktastical | CC BY-SA 4.0 |