help figuring this schematic out - Page 1
Forum section: electronics / beginners

author: ME
author_rank: Frequent Contributor
timestamp: March 19, 2025, 04:31:12 am
content: on figure 15 of the counter ic datasheet, can i just fit a rotary switch to get all functions and mod my counter , Both docs attached , I cant see if it can be done as having a mental block trying to identifie what bits to connect if that makes sense?

author: jwet
author_rank: Frequent Contributor
timestamp: March 20, 2025, 05:23:37 pm
content: Yes- figure 15 uses busses that make it less obvious as to what going on. The left function swtiches use an input on the chip and the digit drives to select functions, the time swtich does similar with another input. Table 1 in the data sheet shows which connection to make for functions and time bases. This saves a lot of pins on the chip, as it cycle though the digits it can also look at the swtich inputs too. A time switch and a function switch tied between the digit drive and those inputs is all you need. I think Maxim make the same part and might have a better data sheet- these are very old parts...

author: MathWizard
author_rank: Super Contributor
timestamp: March 20, 2025, 05:43:51 pm
content: So how would something like this in frequency mode, compare to a modern, affordable DSO, like a 100MHz Siglent/Rigol/etc ?That 100MHz input amplifier looks interesting, I'll have to try that in LTSpice. Someday I want to make a proper digital counter, and I'll probably use an STM32 chip, and if it works any good, then I could try with a faster MCU or design.

author: jwet
author_rank: Frequent Contributor
timestamp: March 21, 2025, 01:18:49 pm
content: >how would this compare to a modern counterNot very favorably, though it would certainly work. This is the way frequency counters in the 70's were designed if they weren't discrete logic. These big counter IC's were one of the first CMOS LSI logic applications along with DVM Chips developed by Intersil in the late 70's. The counter IC itself runs up to 10 Mhz. You'll see a 10x bipolar prescaler in the circuit that gives it 100 MHz- this architecture is still common but the breakpoint in usually >150 MHz vs 10 MHz.Like most things, there have been a lot of improvements in counters. Modern IC processes expanded speeds to GHz. Processors with some math capability allow for reciprocal counting- this measure periods and inverts the value to give frequency at lower frequencies. The preamp sure has a lot of parts- I don't have any opinion on that. Best bet is a new Rigol, etc or an old HP or Racal Dana. I like the Racals because they don't use all customs and you have a chance of servicing them.

author: ME
author_rank: Frequent Contributor
timestamp: March 22, 2025, 11:23:44 pm
content: I wanted to know if i can get the other options like display period etc by using a multipole rotary switch?., It seems the chip can do a lot more than jus display a frequency.

author: Benta
author_rank: Super Contributor
timestamp: March 23, 2025, 12:34:04 am
content: It's quite simple.You need:a 6-position rotary switch for function selection.a 4-position rotary switch for timebase selection.I'm surprised this IC pops up. I built my first frequency counter with it in the early '80s, running up to 650 MHz. I thought it's obsolete since 30 years.

author: jwet
author_rank: Frequent Contributor
timestamp: March 25, 2025, 03:55:16 pm
content: Quote from: ME on March 22, 2025, 11:23:44 pmSorry, got too detailed for you. Of course. The main LSI has "Universal Counter" functions built in, functions like period, totalize, time interval, etc. If you connect the display lines to the correct inputs as in table one, you'll get those functions. Its up to you to make sure that something sensible is on the inputs for the counter chip to work with.