land line phone repeater by johnroy22222

Last crawled date: 3 years, 2 months ago

This is a work in progress fast flashing light repeater for a land line.
I ve done this for my deaf mother in law.
No separate power supply. Just a RJ11 phone plug.
Tested ok on my line.
The current schematics doesn't use zener diodes or a regulator. It uses a 0.68uF X2 275VAC in order to not interfere with the phone line, then a bridge rectifier, then a second stage that is mainly a 470uF 25V capacitor, a 555 IC circuit oscillator and a 5V usb led.
The reason i used the 555 oscillator is the led wasn't flashing fast enough to catch the attention. And catching the attention is the whole purpose of this design !
And i ve been struggling to "step down" the input 70V AC into a acceptable low voltage for the USB led. The 470uF capacitor and the load itself did the job.
A quick list of components i used is :
RJ11 doubler (so the land line can still be normally used)
-0.68uF X2 275V AC
-10nF
-12k ohm
-3.9 kohm
-470uF 25V
-10uF 25V
Things to improve for V3 :
1) Print the back sliding panel access separately (couldn't detach it...) or just suppress this option (it's easy to encase the usb plug in its slot before closing the box)
2) The cover requires some plastic cable ties (ugly) : The 0.2 mm play for the top cover to slide on the bottom part is ok, but the 6mm height may need to be increased (for more friction) or screws added to the design
3) The led itself would take advantage to go deeper in the box (aesthetic)
4) Find a way for more brightness
5) Encapsulate the printed design is something much better looking (the bottom of a rocket... a funny character with funny eyes, a star trek ship...)
V2 has only one difference : on the top cover, the USB slot is moved forward by 3mm because it kept the plug from making good contact (not printed, no tested though)