Jump to content
Due to a large amount of spamers, accounts will now have to be approved by the Admins so please be patient. ×
IGNORED

74HC221 project


Recommended Posts

Probably not what you want to hear but it looks an ideal application for an Arduino or PIC solution?

 

I'm not sure i follow, This is controlled by a Mame PC with a Menu Frontend. [i'd better add that in somewhere!]

Just prior to running the game, The wrapper script simply enables the coin device via LPT, Pacdrive or any other PC IO card.

 

The PC already is doing the part of an Arduino or PIC microcontroller, Unless I'm missing something?

Link to comment
Share on other sites

  • 10 months later...
since the 221 is not directly driving a load (ie using transistors to drive the loads) then consider using a 74HC221 - its a lower power CMOS part with a wider operating voltage range

 

I have decided to finally finish this circuit.

 

As you suggested, I am now using the 74hc221.

My circuit is working well but I'm not very experienced.

 

Do you mind me asking a few basic CMOS related questions?

 

The 74hc221 I am using seems to indicate output of 20mA max.

With typical test/usage of upto 4mA (I only plan to use ~2mA).

http://noel.feld.cvut.cz/hw/st/1924.pdf

 

Does this sound correct or have I got it wrong?

 

One last question I'm unclear about.

From what I understand the 74hc series can drive LSTTL which would mean it sinks on low output.

Is this correct?

Link to comment
Share on other sites

it sounds about right, although the 4ma if I read it correctly (a quick glance only) is for a possible fanout to upto 10 LSttl inputs for a typical 4.5v logic high.

refer to the HCT_USER_GUIDE.pdf, Phillips, nov 25, 1997 - you should be able calculate the relevant figure using the details in that HCT family guide.

the guide refers to source/sink - section 8 ?

 

also, you may be able to save some mA by increasing the base transistors in the bcxxx transistors by moving upto 10k - depends how hard you are wanting to drive the transistors.

Link to comment
Share on other sites

it sounds about right, although the 4ma if I read it correctly (a quick glance only) is for a possible fanout to upto 10 LSttl inputs for a typical 4.5v logic high.

refer to the HCT_USER_GUIDE.pdf, Phillips, nov 25, 1997 - you should be able calculate the relevant figure using the details in that HCT family guide.

the guide refers to source/sink - section 8 ?

 

also, you may be able to save some mA by increasing the base transistors in the bcxxx transistors by moving upto 10k - depends how hard you are wanting to drive the transistors.

 

 

Section 8 of the HCT_USER_GUIDE.pdf should be helpful once I comprehend the relevant bits.

I still don't quite understand the specs on fanout. ie. it's sink/source limits.

 

Thanks for your help.

Edited by ozfalcon
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...