A/D Converter related question

[appleseed]

Hello everyone...

Take a look at this A/D converter circuit. I have this question:
What is the purpose of the 74374? And What is the Bus Enable Port?

 

[Papabravo]

The 74374 is a transparent latch which holds the output data from the counters. The bus enable port controls the three state drivers on the outputs. When it is low the the outputs are high or low according to their contents. When it is high the outputs are in a high impedance condition and do not source or sink current. Multiple tri-state outputs can be connected together as long as only one at a time is enabled.

That Forrest Mimms sure is a bright guy -- isn't he?

 

[appleseed]

ok so what is it exactly that the circuit transforms into a digital signal?

 

[Nigel Goodwin]

ok so what is it exactly that the circuit transforms into a digital signal?

Like any A2D it takes a DC voltage at the input, and converts it to a digital representation of that voltage. Presumablt it's got a 5V range?, so zero volts will give b'00000000' and 5V will give b'11111111' outputs.

It's a very crude project though, it would be a lot simpler to do it in other ways.

 

[Dr.EM]

I put up another post about using an ADC0804 for a possible project. It is about £3 and probably works better? Although this is an interesting design.

 

[Papabravo]

The original circuit (circa. 1973) does show the internal works. It would of course be impractical to use in an actual application.

 

[appleseed]

in what external means can one demonstrate the output?

 

[Marks256]

LEDs would work.

 

[appleseed]

what if one connected the output data from the counters directly to leds?
What would be the problem with that?

And something else, would the current from the 74374 be big enough to light the leds?

 

[Dr.EM]

Use larger than normal resistor values (1.5k?), the LEDs may be dim, but you should get what you need from it.

 

[appleseed]

i think a normal resistor would be 150Ω

 

[appleseed]

b2 spice doesnt have the tl507. maybe its under another name?
or does anyone know where i can find part libraries?

 

[appleseed]

or at least does anyone know what chip should i use instead of the tl507 because i cant find it anywhere?

 

[Nigel Goodwin]

or at least does anyone know what chip should i use instead of the tl507 because i cant find it anywhere?

It's a antique chip, so it's not likely to be available - but as you've never suggested what you want to do, how can we make suggestions?.

 

[appleseed]

the design i attached in this thread... thats what i want to do. but i need to replace the tl507.

 

[Nigel Goodwin]

the design i attached in this thread... thats what i want to do. but i need to replace the tl507.

That's not a reason, if you want to do that design you require that specific chip. To move to a different chip requires a completely different design, and we need to know what you want to do with it.

 

[appleseed]

nothing specific, i just need to present this circuit in a class and it has to be working...

 

[Nigel Goodwin]

nothing specific, i just need to present this circuit in a class and it has to be working...

Well pick something specific! - how were you planning showing it's operation? - are you limited to old technology?, or can you use micro-controllers?.

 

[appleseed]

i was planning on showing the output on 8 LEDs actually.
there is a limitation to the 74LSxx family mainly.

 

[Nigel Goodwin]

i was planning on showing the output on 8 LEDs actually.
there is a limitation to the 74LSxx family mainly.

Well I don't think there's ever been a 74 series analogue converter?, what is the actual specification for your project?.