As an introduction to analogue electronics I have to design a simple alarm system, starting with a power supply.
I would like to add a small circuit that indicates whether or not a fuse is working correctly. A green LED for a working fuse, a red one for a blown fuse. Now I found a small little circuit, shown in the link below, but i have some questions:
http://www.next.gr/meter-counter/meters/fuse-tester-with-leds-l8305.html
1) Why have they chosen a 5.1V Zenerdiode? And what would be the effect of changing this value? (in general, how doess the Zener funtion in this circuit?)
2) The shown circuit is designed for 230Vac, if i want to adjust this for 12Vac, do i have to anything besides the value of R1?
3) In the circuit the LED's only draw about 2mA. Is there a reason behind this choice? Why not just the more normal 10-20 mA?
Any suggestions for a better circuit are ofcourse always welcome. Preferably with a little bit of explanation since i'm a complete beginner.
Thank you,
Nico
I would like to add a small circuit that indicates whether or not a fuse is working correctly. A green LED for a working fuse, a red one for a blown fuse. Now I found a small little circuit, shown in the link below, but i have some questions:
http://www.next.gr/meter-counter/meters/fuse-tester-with-leds-l8305.html
1) Why have they chosen a 5.1V Zenerdiode? And what would be the effect of changing this value? (in general, how doess the Zener funtion in this circuit?)
2) The shown circuit is designed for 230Vac, if i want to adjust this for 12Vac, do i have to anything besides the value of R1?
3) In the circuit the LED's only draw about 2mA. Is there a reason behind this choice? Why not just the more normal 10-20 mA?
Any suggestions for a better circuit are ofcourse always welcome. Preferably with a little bit of explanation since i'm a complete beginner.
Thank you,
Nico