Timeline for How to fade LEDs switched by a 555 timer when supply is cut
Current License: CC BY-SA 3.0
22 events
| when toggle format | what | by | license | comment | |
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| Oct 26, 2017 at 13:08 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Sep 23, 2017 at 17:29 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Aug 23, 2017 at 4:06 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Jul 20, 2017 at 13:03 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Jun 18, 2017 at 22:29 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| May 7, 2017 at 18:38 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Apr 8, 2017 at 2:23 | comment | added | D.A.S. | I=420mA @ 12V (5W total) and ~0A @ <6V 4 sec ramp time from 12 to 6V? Is the "Occupancy Sensor" fast attack motion detect? | |
| Apr 8, 2017 at 2:10 | comment | added | D.A.S. | @shellusr What is load current , Vf and desired fade time? | |
| Apr 7, 2017 at 9:30 | answer | added | Macit | timeline score: 1 | |
| Apr 7, 2017 at 8:10 | answer | added | D.A.S. | timeline score: 0 | |
| Apr 7, 2017 at 3:07 | history | edited | Chris Slothouber | CC BY-SA 3.0 |
updated schematic diagram, updated question to reflect probable impossibility of my question as posed
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| Apr 7, 2017 at 0:34 | history | edited | Chris Slothouber | CC BY-SA 3.0 |
fixed schematic image again
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| Apr 7, 2017 at 0:27 | history | edited | Chris Slothouber | CC BY-SA 3.0 |
corrected schematic image
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| Apr 5, 2017 at 21:07 | history | edited | Chris Slothouber | CC BY-SA 3.0 |
edited title
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| Apr 5, 2017 at 20:58 | comment | added | Chris Slothouber | @JackCreasey Agreed. Though with the goal of developing a better understanding of analog logic, I approached this project with a self-imposed design constraint of no micro controller. I'm comfortable with MCU hardware and software design, but beyond basic interfacing, analog is mysterious to me and I want to know more about working with it. In this case for a one off night light project for my grandmother, it just works. No code to mess around with. | |
| Apr 5, 2017 at 20:55 | comment | added | Chris Slothouber | @TonyStewart.EEsince'75 I added the 1000uF on my breadboard in parallel with the 470uF, as well as at the supply for the LED (CONN_01x02, net labels did not print -- pin 2 of Q5 drains to the connector). With 1m of LED, the fade was a fraction of a second. | |
| Apr 5, 2017 at 20:52 | comment | added | Chris Slothouber | @TonyStewart.EEsince'75 For testing, I am using 1m of 12V led strip, which draws 150mA. Final application will use 2.8m of LED strip, roughly 420mA. LEDs light at >6V (3 in parallel with 150Ω). 4 second drain from 12V to 6V is thus the objective. This gives the occupant of the room time to trip the motion sensor before it goes completely dark. | |
| Apr 5, 2017 at 3:45 | comment | added | Jack Creasey | I'm aghast that anyone would try to do this with a 555 timer and analog logic like this. This is a job for $1.50 MCU. | |
| Apr 5, 2017 at 3:12 | comment | added | D.A.S. | where is 1MF ? 1000 uF? I see C5 470uF. If load is 1A LEDs that is 3S x 3V or 3 * 3W , this has ESR of 1Ω , thus 1000 uF decays LED current ramps down << 1 millisecond. capiche? So if my assumptions of your application are close, not possible. If wrong and 12V stays on but you just want a slow disable off, answer above queries and clarify response. | |
| Apr 5, 2017 at 2:56 | comment | added | D.A.S. | Ramp down requires significant Cap storage energy for low ESR LED's and low tolerance to voltage decay. What are your specs for decay time, LED power. Vmax-Vmin and thus C required to meet T is strongly dependent on LED ESR * C and decay voltage tolerance. e.g. ESR * C=8T implies a huge cap for 10% voltage decay. What load, ramp time and ΔV? | |
| Apr 5, 2017 at 2:16 | review | First posts | |||
| Apr 5, 2017 at 2:27 | |||||
| Apr 5, 2017 at 2:14 | history | asked | Chris Slothouber | CC BY-SA 3.0 |