hospital bed driver board...

i found a driver board from a hospital bed. looks like it had a display/ remote, and control for angle etc of seat(so motors).

it has a the following: Intel 8051 - Microcontroller

LM2940 - 1a vreg

ADC0834BCN -Analog-> digital converter

LM324AN - Op amp

MC74HC244AN - Octal 3-STATE Buffer, what is this?!?!

DS1232 - MicroMonitor Chip, prevents "out-of-control micro" and resets on power failure

4N35 - optocoupler, separates a high an low voltage circuit?

first of all, what is the "MC74HC244AN"? what can it be used for, motor/LED controller? and then, except for the first two items, what are some projects or circuits etc i could built with these ICs? Arduino or not related...


sirbow2: first of all, what is the "MC74HC244AN"? what can it be used for, motor/LED controller?

It was probably used as an interface between the microcontroller and H-bridge. These Solarbotics tutorials will eat your brain for a bit.

Here's an interesting little bug that you can make with it:

MC74HC244AN - Octal 3-STATE Buffer, what is this?!?

It was used as the input / output port for the Intel 8051 - Microcontroller.

MC74HC244AN - Octal 3-STATE Buffer, what is this?!?!

It wasn’t quite as ubiquitous as the 555 but the 74LS244 was a very popular TTL buffer back in its day. It basically consists of eight (hence the OCTAL) amplifiers with a gain of 1 packaged in a single chip. You could ‘turn it off’ effectively disconnecting the outputs (hence the term 3-STATE). It was frequently used to ‘buffer’ or protect the output of expensive microprocessor chips as Mike has pointed out. The 74LS240 was pin-for-pin compatible but had an inverted output. The HC version that you have is a high speed CMOS version (hence the HS) in the middle of the part number whereas the LS version was a low-power schottky version. The prefix (MC) typically identifies the manufacturer and the letters at the end (AN) typically denote the package and other variations. Check out wikipedia for more on this (


what do you mean by inverted? what does it do differently than the 240 version?

Inverted means you put logic one in and get a logic zero out. Where as a logic zero in gives a logic one out.

cool, just liek when i was messing around with floppies...

so all it does is "extend" the ports so that if something gets surged, its the chip that fries, not the arduino(or 8051 etc)?

No it acts as an input or output port on the processor letting external signals onto or out of the data bus when it is activated.

Well it does wind up ‘protecting’ the microprocessor. It is essential in terms of what Mike is saying and has the added side effect of protecting the relatively expensive microprocessor at the same time.
When we switched from an 8085 system with buffer chips to the 68HC11 without them our students learned that the expensive way.


ok. so is it really any use anymore?

ok. so is it really any use anymore?

They are still selling them …