I have made simple led voltage tester that its made with only leds and resistors without using any IC chips or transistors and btw it work also without batteries.
For making you need 19 color leds and 8 1.5kohm resistors,plastic tube for case and aligator clip for ground.
How to Make LED Voltage Tester (work without batteries) ─ Hacktuber
<style>.embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }</style><div class="embed-container"><iframe src="https://www.youtube.com/embed/wAqIco9_Oaw" frameborder="0" allowfullscreen></iframe></div>
