Power supply

[Guest AdamB]

so i modifyed the way the modules are powered, they are not powered by the core module, i built the power supply om a seperate board and will run power from that to each module.

so my question is this, the wall wart  puts what says os 9.2vac 700ma but my multimeter says it puts out 16vac and after going thru the circuit, its between 6.5vdc and 9vdc.  and actualls seems to slowly creep up(8.53-8.58 in about 15 seconds)

WHY??????

Adam

[TK.]

The same link for you: see the "internal resistor" section under

http://www.nzart.org.nz/nzart/examinat/amateur%20radio%20study%20guide/Course%20Files/Power%20Supplies/STUDY%20NOTES%20-%20POWER%20SUPPLIES.htm

Best Regards, Thorsten.

[Guest AdamB]

so whats happening is as my meter uses power it load on the PS increases so the PS puts out more voltage? is that y ir creaps up?

Adam

:)

[TK.]

Yes and no. Your meter doesn't cause a noticable difference, because it's internal resistance is about 10Meg and higher... but the load caused by digital circuit is not linear and varies so fast, that only the average value is meaningful.

However, the purpose of the 7805 is to regulate these effects, so that the whole circuit is supplied with stable 5V

Btw.: don't forget to connect the grounds (Vss) of your power supplies together!

Best Regards, Thorsten.

[Sephult]

Hello!

I am having some problems with my power supply, It seems to be regulating at 5.04v, but I am unsure if my current is correct.  I am having problems getting measurements for current off of the powersupply. It seems that my handheld multimeter might be loading what little current I do have. I was taught to measure current by inserting it in series with the circuit, but this is not working for me. Any suggestions?

It seems that the 7805 gets increasingly hotter when I check current at higher ratings.