Timeline for Implementing LM339 comparator to count analog peaks
Current License: CC BY-SA 3.0
23 events
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| Mar 21, 2017 at 3:29 | history | edited | Trevor_G | CC BY-SA 3.0 |
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| Mar 20, 2017 at 12:52 | comment | added | Trevor_G | @NathanWolanin, See edited answer for an alterative method which gets rid of that capacitor and probably provides a better solution for the larger input. | |
| Mar 20, 2017 at 12:50 | history | edited | Trevor_G | CC BY-SA 3.0 |
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| Mar 20, 2017 at 1:44 | comment | added | Trevor_G | digikey.com/product-detail/en/murata-electronics-north-america/… | |
| Mar 20, 2017 at 0:39 | comment | added | Nathan Wolanin | Ok, I am having trouble finding a plain ceramic cap in 1uF, is there a common alternative or am I paralleling 10 of the .1 to get there? | |
| Mar 19, 2017 at 13:38 | comment | added | Trevor_G | @NathanWolanin OH..wait, I was doing the frequency range wrong. You DO NEED that 1uF up front. .1uF will seriously attenuate idle frequency. | |
| Mar 19, 2017 at 13:37 | history | edited | Trevor_G | CC BY-SA 3.0 |
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| Mar 19, 2017 at 3:42 | comment | added | Nathan Wolanin | ah the joys of being a total newbie.... part of my breadboard was not powered, its basically 4 boards connected. Now it is all powered and I am getting a steady 4.5v output when it is on, so thats something. The signal is not pulling it down yet, the input signal is still attenuated too far. experimenting with a lower voltage divider now. | |
| Mar 19, 2017 at 2:47 | comment | added | Nathan Wolanin | edited original post to show scope from your circuit. It looks like I have dropped the input voltage too much, looks to be about 1 volt. going to reduce the original voltage divider some and see what that does. | |
| Mar 19, 2017 at 0:55 | history | edited | Trevor_G | CC BY-SA 3.0 |
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| Mar 19, 2017 at 0:37 | comment | added | Trevor_G | @NathanWolanin btw I simulated that circuit with 0.1uf it seems ok, though my interpretation of your input signal may be off. (You may have to tweak the voltage divider at the front too because of that) Also you may need to drop the 100nF down to 10nF if your frequency gets up too high. | |
| Mar 18, 2017 at 23:37 | comment | added | Trevor_G | 1N34A is good. You can start out trying with just the 0.1uF first. It may cut off the low frequencies, but not sure what your low end is. If it does, add more .1s in parallel. You can't use electrolytics for ac signals either unfortunately. | |
| Mar 18, 2017 at 23:30 | comment | added | Nathan Wolanin | Ok for caps in 1microF, they only had only had metal film 250v 10% caps. I got those plus .1microF hi-q ceramic disc caps. Figured maybe i can string those together in a pinch. They also had 4.7microF electrolytic so got a couple of those. For diodes, they had 1N914/1N414B switching, GP15M/1431 rectifying, and 1N34A germanium. Any of that lot work for this? Thanks for all the advice so far! | |
| Mar 18, 2017 at 22:17 | comment | added | Trevor_G | These diodes are schotky diodes, they have a smaller forward voltage though the exact model# isn't too critical here. You should not use a Tantalum though, they are polarized, use a ceramic capacitor or similar instead. | |
| Mar 18, 2017 at 22:04 | comment | added | Nathan Wolanin | Just got to the shop, getting after it now. How critical is it to use those exact diodes, 1N5817? The closest I have on hand is 1N4001. Also, can I use a tantalum cap for the 1 microfarad cap in the beginning? I can go to the shack again if necessary, its not too far away. | |
| Mar 18, 2017 at 3:39 | history | edited | Trevor_G | CC BY-SA 3.0 |
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| Mar 18, 2017 at 3:20 | history | edited | Trevor_G | CC BY-SA 3.0 |
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| Mar 18, 2017 at 3:15 | comment | added | Trevor_G | Try the extra divider on the front as I edited. @NathanWolanin | |
| Mar 18, 2017 at 3:15 | history | edited | Trevor_G | CC BY-SA 3.0 |
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| Mar 18, 2017 at 2:23 | comment | added | Nathan Wolanin | Trevor, thanks so much for the help, we tested this with a 1.6v battery and at least got a high output, however, before we hooked it up to the engine we decided to scope the connections one more time, since we did not do it initially... trust but verify. Turns out they had 1x set on scope and 10x set on probe so voltage is actually oscillating between +18 and -16 or so. So now we are back to drawing board, would your schematic scale that much? | |
| Mar 18, 2017 at 2:18 | vote | accept | Nathan Wolanin | ||
| Mar 17, 2017 at 20:43 | history | edited | Trevor_G | CC BY-SA 3.0 |
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| Mar 17, 2017 at 20:34 | history | answered | Trevor_G | CC BY-SA 3.0 |