Digitally controlled LED stroboscope - circuit review - Page 1
Forum section: electronics / beginners

author: Godot
author_rank: Contributor
timestamp: July 11, 2017, 02:42:17 pm
content: Hello!I am building an Ardunio-based LED stroboscope. Later I'd like to share the design on Instructables. As I want this to be a good beginner project, the aim is to be cheap (as it stands now, the whole thing will be under 10$), and as simple as possible.I have tested the circuit below on breadboard, and it works perfectly up to at least 100kHz (yes, it's still a strobe...) I would be glad if you could review both the circuit and the shematics itself, as I am still learning to make these. Is there something I should add? Is there anything I can remove/simplify? Is the shematics easily understandable? What would you change?Notes:The circuit is powered by four AA battery, up-converted to 12V using this buck-boost converter from eBay:http://www.ebay.com/itm/1PCS-MT3608-Step-Up-Power-Apply-Booster-Module-DC-DC-2V-24V-2A-BBCA-/311719940869?hash=item4893f4d305:g:13cAAOSwbdpWaOlRThe cross-line on it's symbol meand to symbolize that IN- and OUT- are internally connected.pin 9 outputs a 0-5V PWM signal, with it's frequency and duty-cycle adjusted via the rotary encoder (pin A, B, C) with button (pin E, D)The PWM's frequency is adjustable between 0 - 100kHz (with cca. 0.5% accuracy), the DC is 0.1-50%.The LED is an array salvaged from an LED-bulb. I found it's nominal current to be around 150mA.

author: mariush
author_rank: Super Contributor
timestamp: July 11, 2017, 05:04:09 pm
content: I guess it would work for your needs.What I don't like is having your LM7805 regulator AFTER the 12v boost circuit. I guess it's good to provide a minimum load to the boost converter, and since your arduino most likely uses only a few mA the losses (12v - 5v ) x ? mA are not big.You kinda need 5v because of the irfz44n requiring at least 4v Vgs, but 5v would be better.I would have looked for a better mosfet to use a 3.3v .. 3.6v ldo directly to the batteries and power my arduino like that.Also, I don't think it would hurt to have a capacitor at the output of the 12v boost converter (but probably the boost converter already has enough capacitance on the output by itself)

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 12, 2017, 03:25:45 am
content: What purpose the stroboscope is?

author: Godot
author_rank: Contributor
timestamp: July 12, 2017, 12:08:56 pm
content: Quote from: mariush on July 11, 2017, 05:04:09 pmYou're right. The reason I did it this way is to easily make it 12V-powered.Quote from: mariush on July 11, 2017, 05:04:09 pmC1 is on the converter's output. Do you suggest to make it bigger?Quote from: Mechatrommer on July 12, 2017, 03:25:45 amNothing too serious.Pretty much for experimenting, maybe some frequency measurement. The most serious thing I plan to use it is to view the shape of some audio-frequency vibrations.

author: StillTrying
author_rank: Super Contributor
timestamp: July 12, 2017, 12:37:08 pm
content: You'd need a lot more uFs of decoupling especially near the mosfet/led.In the physical circuit I'd always have the positions of R1 and the LED swapped.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 12, 2017, 03:59:48 pm
content: Quote from: Godot on July 12, 2017, 12:08:56 pmback in the school, we used stroboscope light to get the marine propeller speed in controlled lab condition. other applications are photography long and multiple exposure and some experiment relating to rotating machines and vibration mechanic, as you've put it, we can also verify china brand laser rpm measurement device (that i own one), being a photography and mechanical background, that a few i can think of. this can have some other applications, you remind me of this. a simple circuit that can have practical applications. i wonder we will need good freq resolution for this to be usefull. anyway good luck.