I have begun prototyping for a 125khz repeater to complement my other project 13.56mhz Repeaters. I likely wont be making all of the files of this project open source but i will release some of the gerbers as i get there.
Goal
To Create a successful 125KHz low frequency repeater circuit.
I have a current design out to the fab house to see if this is viable.
Current Design:
Trace Thickness: .1mm
Trace Spacing: .1mm
Turns Per Layer: 57
Number of layers: 6+2 (top and bottom layers)
Estimated Thickness: .8mm
Overall Diameter: 40.6mm (1.6in)
This design will be dirty. but it will let me know if i am on track and if i should continue this project.
Flex Sticker Possibility?
Ive ran as many different designs and combinations of designs as i can think of. Unfortunately i will never be able to get this into a flex sticker style. I either do not posess the design ability, nor do the fab houses i use have an ability to have multi-layered Flex boards that will not price out a normal user. Maybe in the future if manufacturing costs go down it can become a possibility however for now it just will not be feasible with my current capabilities.
After some back and forth with the fabhouse i have some changes.
JLCPCB (The fab house i use) seem to have conflicting specification restrictions. Initially when i designed this i designed it with .1mm wide traces and .1mm wide spacing per their minimum specifications for multi-layered boards. Apparently that is incorrect and it is .15mm so i had to recalculate everything…
I have opted to go with two seperate designs. a small and a large. Due to the fabhouse’s size restrictions the price goes up significantly once you get larger than 50mm on a 8layer pcb. As a comparison… to get the small board prototyped its costing arounf 35$ shipped with 5 units. to get the large one prototyped im at 115$ for 5 units. This, if successful unfortunately will be pricey to mfg, The only solace is that i have the possibility of reducing overall costs for the large unit by making it passively functional. still though I have some desgins choices that i worry will affect the functionality of these repeaters and there is a high liklihood that they will not function.
So here are the current prototype specs in case the viewers at home want to play.
125K Large (possibility to make this device passive)
Intended Capacitence: 30pf
Intended inductance: 53921.7uh
Layers: 8
Turns per layer: 76.5
Trace Thickness: .15mm
Trace Width: .15
Center Diameter: 20mm
Total Size: 70mm (2.7in)
125k Small (Impossible to make passive atm)
Intended Capacetence: 100pf
Inductance: 16249uh
Layers: 8
Inner Diameter: 6mm
Total Turns: 424
Turns per layer: 53
Trace Thickness: .15
Trace spacing: .15
Size: 41mm (1.614 inches)
and as stated before. These designs will be impossible to convert to flex with the current limitations.
Ive never returned a donation but it isnt necessary as i am interested in getting this completed as well.
The only reason i am being transparent on the mfg prototyping costs is because these are going to be niche units and will likely be more costly than its 13.56mhz big brother.
here you go you fuckers!!!"