Timeline for Critique please - Arduino switching/dimming 24 V LED strip using 20 kHz PWM
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
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| Mar 25, 2023 at 8:09 | comment | added | Edin Fifić | @Polynomial You're right, it could definitely use a better driver, at least an NPN-PNP pair after R1. | |
| Feb 7, 2023 at 4:48 | comment | added | Polynomial | The gate driver circuit is still fully broken, though. A MOSFET with that much input capacitance needs a proper driver. | |
| Feb 7, 2023 at 4:46 | comment | added | Polynomial | Ah, good point about the MLCCs on the strips, I wasn't thinking straight there - you're right, it needs to be from +V to GND outside of the MOSFET, not across the strip itself. Not due to surge currents, but just because it'll stop the PWM from working properly. Still, though, I'd just omit C3 - the impedance of the power delivery path should be low enough, so there's no need for decoupling unless there's an expectation of massively long power leads with tons of parasitic inductance. | |
| Feb 7, 2023 at 4:44 | comment | added | Edin Fifić | Wouldn't caps on strips increase the surge currents? Maybe an RC snubber across the voltage rails on strips? The 470uF here was just some bare minimum for the control circuit itself, not really trying to meet the surge demand of the strips. Their resistance plus any additional wire resistance is likely more than the ESR of this capacitor. | |
| Feb 7, 2023 at 4:41 | comment | added | Polynomial | The IRF3205 also has a huge input capacitance - 20 times that of the IRF510. So at lower duty cycles, with R1 being 1kΩ, the LEDs will never actually reach their turn-on current and you'll just be heating up the MOSFET for no reason. | |
| Feb 7, 2023 at 4:37 | comment | added | Polynomial | Careful: C3 needs to have a ripple current rating of at least 5A at the switching frequency, otherwise self-heating (from ESR/DF) will cause it to fail. I'd honestly just omit it entirely unless there's a demonstrable need for additional bulk decoupling, and even then I'd consider using ceramics (MLCCs) on the LED strip itself for localised decoupling instead. | |
| Feb 7, 2023 at 3:57 | history | edited | Edin Fifić | CC BY-SA 4.0 |
Improved explanations with additional words
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| Feb 7, 2023 at 3:47 | history | answered | Edin Fifić | CC BY-SA 4.0 |