How to get 7493 to work

7493.pdf (360653Bytes)

i have been trying for the last few nights tyring to get my counter to work

the wireing should be correct ,


grnd- ground

input a, to pin 9 on the arduino and it is set to a constant 150 PWM

input b - connected to Qa

Qb, Qc Qd, to LEDs

do i need to hook up the R pins?

i know the PWM works

and there is power going to the chip

but no counting is going on, so any help would be appreciated


Part of your problem there is that your standard 7493 (facts sheet here) needs to charge for 60 minutes before you can get anything from it.

Of course, I jest. BUT it is important to know which breed of 7493 you have. On my HCT variant, for example, pins 8, 9, 11 and 12 are OUTPUTS and I wouldn’t attach a PWM to them. It has no R pins (is this the same as HR?) There are different Vcc variants, too.

PWM? What’s PWM got to do with anything? Is that simply the mechanism to get the Ard-whine-oh to output a square wave pulse train? Did you try a 50% mark to space ratio?

Be aware, also, that some types are fussy and need their unused inputs tied to Vss or Vdd. (Probably irrelevant as you appear to be using input B to cascade the two counters.)

I can probably help if I know the flavour of the beast.

What do you mean by 150pwm?

What do you mean by 150pwm?


If you read the datasheet page 4: you can see that you should connect Q0 to CP1 and MR1+MR2 to GND.

i uploded the data sheet

i uploded the data sheet that I am referancing and ill try changing the cycle to 50%

what i mean by r pins there are reset pins on 2 & 3

ill keep trying





150/255 for the analog write

150/255 for the analog write function

and that datasheet is similer to what i am using except that mine is just a decade counter

Same stuff
Just as jka states, if you check page 6 of your datasheet, at least one of the RO(1) or RO(2) pins needs to be low for the counter to operate, and probably best to ground both. And if it is a 7493, then it’s a binary counter, the decade counter is part number 7490. The other connections you have sound fine.

Here is a guide to the 7493:
Here is a guide to the 7493:

you are righ tit is a binary

you are righ tit is a binary counter, i just get those 2 chips confused because i have 7490 as well

ok i have the LEDs lit up on the counterand iknow its counting i can see one led flashing a bit

now the question is how do i slow the count down?

slow the input clock to 7493
You slow your count down by slowing the input clock to the 7493. Sounds like you are driving it with a pwm counter timer, so you either increase the max count on the counter (which should slow the output clock) or slow the clock going into the pwm. If you are using the Arduino there is a programmable divider (prescaler) on the pwm clock input. I see it has divide by 8, 64, 256, and 1024 that you can use. But I’m too new to the Arduino to tell you how to do that exactly. Hopefully that points you in the right direction.

i tried chnaging the pwm to

i tried chnaging the pwm to a lower level but still no visible change

and i looked into the prescaler but i havent found any info on it

i will still look, i may have to change to a 555 timer to be able to control the clock better


Apples and Oranges
Are you sure the data sheet you uploaded is the corect one for your flavour of chip? Read me the part number from the top of the chip.

Frequency vs Ratio
I think the chappies might be suggesting a slower FREQUENCY for you PWM rather than a lower mark to space ratio. I know NOTHING of picaxe, but I know my PWM from my square wave… Definitely roll with 50% PWM, but reduce the frequency.

this is how it loks on top

this is how it loks on top of the chip


tesla x58


tha data sheet that i uploaded is the closest to my chip

i could not find the one from the manufacturer