Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits?

[bockman]

Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits?

I have lots of these wall warts lying around. If a wall wart is regulated and linear, and if it has the appropriate voltage and max avail current, is it just as good for powering digital circuits as a power supply I build using a transformer and a 78xx regulator? I'm just wondering if the quality of regulation, the transient response, the noise level, etc, will generally be OK, and if there is any reason to make my own power supplies for circuits I build instead. Thanks.

 

[mvs sarma]

Re: Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits

Welcome to EDA board.
it is preferable to have a wall wart of say 9V or so( even unregulated) with a current of just above 1 amp.
you might use s a 7805 regulator with a suitable heat sink. then the output would suite your digital circuits' need. Perhaps you may see the 7805 dtatsheet for full information. All the best

 

[KJ6EAD]

Re: Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits

If they're regulated, they're usually adequate. I've been using both electromagnetic and switching types for years to power digital circuits with no problems. If a particular supply has too much ripple or can't handle the load, just filter it or grab another. I get switching supplies as high as 45W models at my local thrift stores for just a few dollars each.

 

[mvs sarma]

Re: Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits

i suppose the so called wall warts would not be that bad, and would obviously have suitable filtering. If needed we can always have some filter caps of say and some 0.1uF disc caps also,on either side of 7805.
if the wall wart as per definition is only a transformer ro give stepped down AC, we can have a bridge rectifier and filter in the OP's design converting it to DC.

 

[Tahmid]

Re: Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits

Hi,
If you're sure that the output is regulated 5v, then you can use it perfectly well. Don't worry about the ripple as you could just add a 1000uF capacitor at the output for filtering.

Hope this helps.
Tahmid.

 

[bockman]

Re: Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits

Thanks for the welcome, and thanks for the various replies. Tahmid mentioned that if a power supply had some residual ripple, you could add a 1000uF capacitor at the output for filtering. I thought I read somewhere recently that a large capacitor like 1000uF on the output of a voltage regulator might cause some sort of problem (I don't remember what problem). Is it generally OK to put a 1000uF capacitor on the output of a voltage regulator? Thanks.

 

[Tahmid]

Re: Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits

Hi,
The only problem I can see is if the power supply can't handle the required charging current. But the current needed to charge the 1000u cap is nothing very large, as your power supply can deliver enough current. If you can specify what problem you read about, that may help, but I see no problem with this.

Hope this helps.
Tahmid.

 

[mvs sarma]

Re: Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits

Let the OP come forward with what exactly he has.
Specifications like AC or DC voltage output , capacity in amps.
there is no point is loose discussion that takes us no where but MBs of site space wasted.

 

[bockman]

Re: Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits

OK, thank you all for your replies--I think that's all I needed. I wasn't looking for anything super-specific or super-detailed.
Thanks again--I appreciate it.

 

[mvs sarma]

Re: Regulated Linear "wall wart" AC to DC power adapters OK to power digital circuits

thanks and all the best