I have been working on this project for some time with the help of Bill Marsden. I have built 8 of these timers http://forum.allaboutcircuits.com/showpost.php?p=287856&postcount=7 and mounting board for cooking purpose now I'm trying to power all 8 from one 9V power source but I dont know how many Amp I will need. Should I buy a wall wart or build a power supply? Thanks for your help.

 

I would think a wall wart, then modify it. That or you can make your boxes where they are designed to chain the power supply, a power in and a power out jack. They could even be the same electrically.

I would be amazed if these units took more than 100ma each, they probably use much less. Have you measure it with a ammeter?

If I'm right then 1 amp would be more than enough for all of them.

The voltage isn't that critical either, figure 12VDC is also good, but don't get close to 15VDC. Many wall warts are not regulated (yours doesn't have to be), so a 12V wall wart can output 18V. This is a circuit killer.

While I'm not recommending this one in specific, it is a good example...

http://www.bgmicro.com/65v25aregulatedps.aspx

Look in local thrift shops, you might find what you need there for a $1.

 

I agree with Bill. Measure the current of one of then in operation and multiply by 8 for your total power requirement. I'd add a bit more current to the Adapter requirements so you never get to the adapters max and overheat the thing.

 

In modifying a wall wart, you add 7 more connectors, each with a power jack.