A few of you requested to know how I was driving the LEDs. Here is a simple schematic. The first one shows you how you can drive them with a P Channel MOSFET along with an NPN transistor and the second one shows you how to do it with a single NPN transistor.
On the flash light, I have three sets of LEDs. 18, 12, and 7. Each set controlled by a separate driver.
The VCC here is the LiPo battery output which can be in between 3.6 to 4.2V. The control INPUT can be connected to an Arduino. In my case, it was the Adafruit Trinket M0. You can use a 3V3 version of the Arduino mini instead.
Hope this helps!
@mohitbhoite you using Eagle for your projects?! You using PRO version or student's?!
4:21 AM Jan 13, 2019
@mohitbhoite you can do charlie multiplexing in this project..!
4:48 AM Jan 13, 2019
4:52 AM Jan 13, 2019
5:20 AM Jan 13, 2019
Bro you said you use a MOSFET transistor but the circuit shows that the transistor is a bjt NPN ?!!
5:42 AM Jan 13, 2019
@m.ea14 yes, in the first schematic the p channel mosfet is driven by a NPN transistor
8:31 AM Jan 13, 2019
Where do I get the Pro version of the eagle?
8:58 AM Jan 13, 2019
Was your decision of using these transistors or the MOSFET driven by what you have in the lab?
9:13 AM Jan 13, 2019
What is the reason to use bipolar technology to drive a Mos and not an other mos?
Same question for lowside, why do you use a npn and not a nmos? Is it for CEM considerations? (Or price, or stock reason?)
9:16 AM Jan 13, 2019
Why did you not use the NPN setup, is it because of the power consumption? I got confused why you posted two setups! 😉
11:48 AM Jan 13, 2019
I wish they taught me this in school 😒
12:04 PM Jan 13, 2019
Thank you. What is the constant current value achieved in these schematics
@crowstudio based on something that I had laying around. More importantly, I made a design error in the beginning which made me improvise and use a high side switch instead of a simple NPN transistor setup.