Timeline for 555 Timer Stops working after a few seconds
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
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| Jan 1, 2019 at 23:53 | comment | added | gkunz | @TonyEErocketscientist where do you have that info from? In my TIP121 datasheet, its rated with min 1k and as far as I could tell from my measurements this is pretty accurate at low load and low temperature. | |
| Jan 1, 2019 at 20:19 | comment | added | D.A.S. | This TIP is a Darlington with hFE of 3k~5k so the 10k resistor looks like 2~3 ohms on the emitter > @DanielTork | |
| Jan 1, 2019 at 19:13 | comment | added | Daniel Tork | I think that the base resistor prevents too much current from going through the LED. Also, OP mentioned in comments that the LED can work with up to 15V. I would always add that resistor connected to collector and put the LED on that side, too. I agree that there are better designs. | |
| Dec 31, 2018 at 21:08 | comment | added | D.A.S. | The 200mA is steady but for pulses more is ok, imagine a 2 Ohm Rce in series with driver for voltage drop. Did you try my simulation>/ LEDS are like Zeners with different Vf and series R equivalent circuits | |
| Dec 31, 2018 at 20:20 | comment | added | D.A.S. | Provide datasheet links . Did anything get hot? Use a FET for a 12V switch not a darlington or at least the collector out. | |
| Dec 31, 2018 at 20:19 | history | edited | D.A.S. | CC BY-SA 4.0 |
added 379 characters in body
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| Dec 31, 2018 at 20:18 | comment | added | gkunz | Also the maximum load on the 555 timer output should never exceed 200 mA, which is why I'm using a transistor. | |
| Dec 31, 2018 at 20:13 | comment | added | gkunz | Thanks for your quick answer! The thing is, that this LED system (I believe its a LED strip with some light diffusers) itself must have a current limiter. I'm driving the 12V input of this black box system (I don't really know what's inside). But given the fact, that this system is made of operation using direct 12V DC, doesn't this mean that it already limits current correctly by itself? | |
| Dec 31, 2018 at 20:07 | history | answered | D.A.S. | CC BY-SA 4.0 |