Topics Topics Edit Profile Profile Help/Instructions Help Member List Member List  
Search Last 1|3|7 Days Search Search Tree View Tree View  

555s

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2010 - » Archive through 26 January, 2014 » 555s « Previous Next »

  Thread Last Poster Posts Pages Last Post
  ClosedClosed: New threads not accepted on this page        

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

echase
Frequent Contributor
Username: echase

Post Number: 761
Registered: 07-2007

Rating: N/A
Votes: 0 (Vote!)

Posted on Thursday, 23 January, 2014 - 04:53 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

A colleague has decided to dig up his old design knowledge and design himself a sound to light converter using 741s and 555s. I have found some unused 30 year old ones in my stock and given them to him as I never use them these days. Whether 30 year old unused ICs are reliable is a moot point.

It occurs to me that in the intervening years there have been many improved op amps so hardly anyone uses 741s any more. However the NE/SE555 appears to have few modern updates apart from the CMOS version. Are there any replacements you would recommend for building simple monostables or astables?
Top of pagePrevious messageNext messageBottom of page Link to this message

pebe
Frequent Contributor
Username: pebe

Post Number: 149
Registered: 05-2005

Rating: N/A
Votes: 0 (Vote!)

Posted on Thursday, 23 January, 2014 - 06:17 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Yes, there are lots of op-amps to choose from now with better characteristics than the 741, but it is still OK for many jobs.

I have yet to find an IC that can beat the 555 for versatility. To be able to configure a chip as an astable, monostable or bistable with a 200mA output capability is very useful.

Regarding aging, an engineer from Plessey Semiconductors once told me that the limiting factor was temperature. It seems that there is a slow deterioration due to interaction between the silicon and its leadout wires, and that process is accelerated with increased temperature.
Top of pagePrevious messageNext messageBottom of page Link to this message

atferrari
Frequent Contributor
Username: atferrari

Post Number: 1468
Registered: 05-2005


Rating: N/A
Votes: 0 (Vote!)

Posted on Thursday, 23 January, 2014 - 06:34 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

So, if kept in a fridge thew should last longer...?
Agustín Tomás - Buenos Aires - Argentina
Top of pagePrevious messageNext messageBottom of page Link to this message

gordon
Frequent Contributor
Username: gordon

Post Number: 965
Registered: 05-2005

Rating: N/A
Votes: 0 (Vote!)

Posted on Thursday, 23 January, 2014 - 07:25 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

The 555 is definitely one of the most successful chips manufactured. There is the 4047, but that has also been around for a long time and doesn't have the current drive output of the 555.
Top of pagePrevious messageNext messageBottom of page Link to this message

echase
Frequent Contributor
Username: echase

Post Number: 763
Registered: 07-2007

Rating: N/A
Votes: 0 (Vote!)

Posted on Friday, 24 January, 2014 - 10:54 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Just looked at the date codes on these and they are 35 years old! I actually acquired them from the bin during a laboratory clear-out when I worked at Plessey as a Reliability Engineer, not Plessey Semiconductors though and they are not Plessey manufactured. The big debate then was with the interaction/corrosion between the epoxy packaging and leadframe and damp penetration into the epoxy. Thus for all military applications ceramic packaging was mandated. I am not up to date on this but suspect that ruling got dropped, as suitable epoxies were getting better, except perhaps for space applications.

As leadframe corrosion and damp penetration would be worse if damp I suspect that putting them in a fridge might actually make them worse, unless packed with silica gel. But generally lower temperatures would lower the degradation.

(Message edited by echase on 24 January, 2014)

Administration Administration Log Out Log Out   Previous Page Previous Page Next Page Next Page