What Chip Converts Decimal to Pulse ..?

[Mhz1]

Hello, I'm trying to find out what chip converts Decimal Numbers to generated Pulse Output...?

In other words, If I have a keypad and press the number 5, and want to have 5 Pulses of output, what chips would perform this action?

I guess I would prefer a square wave type Pulse.. But not particular.. Thanks For any Helpful Info In Advance...

 

[surajbarkale]

A microontroller & a few lines of code will be sufficient here. Unless you require very small pulse duration. A digital circuit may also be build by using counters & gate but cost will be higher than microcontroller solution.

 

[Mhz1]

Thanks suraj, but I was looking more for an IC number and type that would perform such a function... know of any?

 

[Kevin Weddle]

First you need an encoder to give you the binary representation. This goes to a multiplexar. The selects can be cycled with a counter that is clocked at the frequency you want. Let's say the clock time is 1 ns. The counter will increment every 1ns. This means the select will change every 1ns. The data will be presented at the output with a pulse width of 1ns.

 

[audioguru2]

Let's say the clock time is 1 ns. The counter will increment every 1ns. This means the select will change every 1ns. The data will be presented at the output with a pulse width of 1ns.

Hi Kevin,
A whole ns? Then your counter will be running at 2GHz.
Isn't that frequency a bit high for a simple keyboard multiplexer?

 

[Kevin Weddle]

1ns is the time of a cycle when talking in terms of frequency. So yes it is a little high but it is 1GHz and not 2GHz. For those used to dealing with pulse width, I am just clarifying this point.

 

[audioguru2]

Sorry, Kevin. You are absolutely correct. Your clock frequency is "only" 1GHz, with your counter incrementing every 1ns.

 

[Mhz1]

So when the Binary number is input to the Multiplexer, the Multiplexer will take that binary number and convert it as the relative pulse count at a certain pin in relation to the clock frequency that is applied to the Multiplexer?

Are there any schematics that support such an operation that I can view? Thanks

The reason I ask, is because there isn't much if any thing over the Internet explaining this chips function in full...

 

[Kevin Weddle]

It is easy to implement this. You just use the standard components. The output will be a train of data with a 1ns pulse width for each bit. When it's done, the next bit will be a repeat of the sequence. A 5 will look like this assuming a 4bit encoder :

0101 0101 0101 0101 until the next number is pressed. The counter will have to be a two bit. A count of 00 will select the 0, a count of 01 will select the 1, a count of 10 will select the 0, and a count of 11 will select the 1.

 

[Mhz1]

Thanks kevin, I think I'm going to need a data sheet of a Multiplexer to fully understand the principle.. I am attempting to make a mechanical movement of a stepper motor that will correspond to movements via a digital keypad.. In other words, if I push key 5, I want the motor to step 5 times ..(Just for experimentation). I want this project to be free of computer input (serial, usb parrallel) and free of microncontroller input..

 

[audioguru2]

Wait a minute, Mhz,
Kevin's counter doesn't output the number of pulses that you want, and neither does his multiplexer.
A counter can be preset by a binary input to a certain number that it starts counting from. Then its outputs count up or down from there. You could preset it to "5" from the keyboard's encoder and have it stop when it counts down and reaches "0". With a multi-input gate connected to all counter outputs and the clock, the output of the gate will be the 5 clock pulses that you want. The same thing will happen with any other keyboard-to-preset number.
One kind of multiplexer simply "selects" multiple inputs and outputs them, one at a time, usually in sequence. Another kind of multiplexer simply "steps" its multiple outputs, one at a time, and has a single input. I don't see any requirement for a multiplexer in this circuit. Kevin says that the multiplexer "selects", but there is nothing to select from, since there is only one keyboard encoder that can directly feed the counter's presets. A keyboard encoder sometimes has a multiplexer built into it, but that is also not required here.
You will need additional circuitry such as a flip-flop and a multiple-input gate from the encoder to start the clock when you press a button and to keep it going until the counter output reaches "0".

 

[Mhz1]

Hello audioguru, and thanks for the info... The question I would like to inject in this decimal to pulse quest would be:

What is it that a standard touch-tone telephone use, when you set it to pulse instead of tone, When you select pulse out for a telephone, you can actually push a decimal digit and actually here the pulse click the number you pushed.. What are they using for this? Thanks for the help..

 

[audioguru2]

Hi Mhz,
Good idea! Why don't you use a telephone dialer IC? Motorola and Philips used to make them.
It will do exactly what you need, and probably can be speeded-up, but not as fast as Kevin's.

 

[MP1]

Mhz,
You are talking about DTMF.

MP

 

[audioguru2]

MP,
No, he is not talking about DTMF, but about the IC in a telephone that can be switched between "pulse" (like rotary dial) and "tone" (DTMF). His application needs the pulse output.
All dialer ICs have DTMF output, but some can also be switched to produce pulse output.

 

[MP1]

ok, I see. I just read it again. Switching between touch tone and pulse.

MP