Sorry for the bad quality of the writing ad of attached images,
but I'm out of exercise, being returned recently from hospital. And computers and photo camera are like little greeen aliens, now.
I wanted to build a 4 decade resistor box (0 to 10 Kohms 0,1 Ohms resolution, , and began searching ALIEXPRESS for the necessary components, 10 position rotary switches, knobs and a suitable enclosure, then I found one ready assembled, at the very low price of 11,05 Euro
It is not bad,and came in a suitable mailingbox, which bears the manufacturer’s name : JiaoXueyiqi, complete with an 8 pages user’s manual (in Chinese), with schematic and application instructions.
I could not find any technical specification (tolerance, andpower handling: there is an indication of maximum current allowable).
It is obviously intended for educational use
The attached images show the product, which is available here :
ttps://login.aliexpress.com/?returnUrl=https%3A%2F%2Ftrade.aliexpress.com%2Forder_detail.htm%3Fspm%3Da2g0s.9042311.0.0.22254c4duy27Rp%26orderId%3D3005125109566444%26tsp%3D1600627413628]]ttps://login.aliexpress.com/?returnUrl=https%3A%2F%2Ftrade.aliexpress.com%2Forder_detail.htm%3Fspm%3Da2g0s.9042311.0.0.22254c4duy27Rp%26orderId%3D3005125109566444%26tsp%3D1600627413628 The first thing I noticed are the binding posts, which have no 4 mm hole for a banana Plug.
They will be replaced soon, with little effort.
The circuit is a single side PCB where the resistors, which seem standard 1206 SMD components, are soldered (hey seeem having been hand soldered, )
The Switches’s contacts seem made with steeel foil (No silver here…) plated with what seem tin (I could solder a wire to it, so it must be tinned).
The schematic is different from those I’ve seen in other decade boxes, because they used less resistors as you can see:
Looking at the x 1K decade, instead of 10 1K resistors wired in series (one per position) here we see a two pole switch and a 5K resistor which,on positions 6, 7, 8 and 9, connects to the other section’ common. Four 1K resistors are wired to positions, 1, 2, 3, 4, , so 6K is obtained with 5 K + 1 K, 8 K = 5K + 3 x1K
It is not bad,and came in a suitable mailingbox, which bears the manufacturer’s name : JiaoXueyiqi, complete with an 8 pages user’s manual (in Chinese), with schematic and application instructions.
I could not find any technical specification (,tolerance,and powr handling: there is an indication of maximum curent allowable).
It is obviously intended for educational use
The attached images show the product, which is available here :
https://login.aliexpress.com/?returnUrl=https%3A%2F%2Ftrade.aliexpress.com%2Forder_detail.htm%3Fspm%3Da2g0s.9042311.0.0.22254c4duy27Rp%26orderId%3D3005125109566444%26tsp%3D1600627413628 The first thing I noticed are the binding posts, which have no 4 mm hole for a banana Plug.
They will be replaced soon, with little effort.
The circuit is a single side PCB where the resistors, which seem standard 1206 SMD components, are soldered (hey seeem having been hand soldered, )
The Switches’s contacts seem made with steeel foil (No silver here…) plated with what seem tin (I could solder a wire to it, so it must be tinned).
The schematic is different from those I’ve seen in other decade boxes, because they used less resistors as you can see:
Looking at the x 1K decade, instead of 10 1K resistors wired in series (one per position) here we see a two pole switch and a 5K resistor which,on positions 6, 7, 8 and 9, connects to the other section’ common. Four 1K resistors are wired to positions, 1, 2, 3, 4, , so 6K is obtained with 5 K + 1 K, 8 K = 5K + 3 x1K
Interesting, they saved 20 resistors ( 4 decades per 5 resistors each) in the whole box…
IF I want better specifications , I can easilyreplace the resistors with better ones,
I tested yhe unit using a My UNI-T UT 61 , and It seem to work according to the specifications.
The switches have a nice feel, and a good click..
The contacts work against the coppers surface of the PCB.
There is misterious transparent “grease” covering the contact area. I did not understood it’s nature and funcction: it seeems glycerine,