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| MOSFETS as voltage controlled gates |
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| SolderOcelot:
I need 3 gates in my circuit which each should close (as in: let current go through source and drain) IF the circuit voltage is > X. My question: Are MOSFETS the right tool for this construction? My goal is to create a LED strip that lights up a number of LEDS depending on voltage. Please take a look at attachment for schematic. |
| ArthurDent:
Here is an IC that is designed for this type of application and I'm sure there are some others. https://www.ti.com/lit/ds/symlink/lm3914.pdf |
| SolderOcelot:
--- Quote from: ArthurDent on November 18, 2018, 12:34:37 am ---Here is an IC that is designed for this type of application and I'm sure there are some others. https://www.ti.com/lit/ds/symlink/lm3914.pdf --- End quote --- On one hand I think it's pretty cool that IC's come onto my path now but on the other hand it's quite a buzzkill to just slap an iC on there and be done with the project. I was hoping to build this a bit more primitively. |
| Whales:
You could use varying amounts of diodes in series to each LED. The turn-on might not be as abrupt as you hope, however. Another alternative is to use diode stacks that then feed the base of an NPN. That might have a sharper turn-on. I suspect FETs would again be too gradual of a turn on. |
| SolderOcelot:
--- Quote from: Whales on November 18, 2018, 01:33:50 am ---You could use varying amounts of diodes in series to each LED. The turn-on might not be as abrupt as you hope, however. --- End quote --- What do you mean with "abrupt"? As in speed in which LEDs switch on or the contrast between the LEDs' on and off state (diffusion). --- Quote from: Whales on November 18, 2018, 01:33:50 am ---Another alternative is to use diode stacks that then feed the base of an NPN. That might have a sharper turn-on. I suspect FETs would again be too gradual of a turn on. --- End quote --- So with "diode stacks" the diodes act as voltage barriers right? So the first stack would require a voltage of 1.3 for current to go through right? If so, I'm worried about the amount of resistence they add to the circuit which would interfere with other features. |
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