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"Help" section and 9 Volt USB

 
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jaredharley
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Joined: 04 Apr 2006
Posts: 9
Location: Greeley, CO
PostPosted: Tue Apr 04, 2006 1:45 am    Post subject: "Help" section and 9 Volt USB Reply with quote
I think the electronics needs a "Help" section for those looking for assistance on their projects.

I, for example, am working on this 9 volt USB charger that was featured in Popular Science. Using both the article and his website, I put everything together. An even 5 volts flows into the USB port, but as soon as I plug in a device, the "on" LED indicator turns off and no power flows to the device. I have no clue what's wrong - any ideas?[/url]
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB
PostPosted: Tue Apr 04, 2006 9:55 am    Post subject: Re: "Help" section Reply with quote
jaredharley wrote:
I think the electronics needs a "Help" section for those looking for assistance on their projects.

I, for example, am working on this 9 volt USB charger that was featured in Popular Science. Using both the article and his website, I put everything together. An even 5 volts flows into the USB port, but as soon as I plug in a device, the "on" LED indicator turns off and no power flows to the device. I have no clue what's wrong - any ideas?[/url]


Welcome jaredharley,

Adding a help section is a good idea, I will probably do that in the near future. Do you have a schematic of the design you built? I took a look at the site you mentioned but could not locate a diagram of the circuit.

If you are using a standard LM7805 here are some standard issues…

* Input voltage is too low. You need about 2 volts more that your output. So make sure that your 9 Volt battery is good enough to provide at least 7 Volts under load. Most 9 Volt batteries can’t provide much current so this is a common 9 Volt issue.

* No capacitors in circuit. You can get away with not using any capacitors sometimes. Some regulators are less susceptible than others, but having input and output capacitors are important. In your case don’t worry about the input cap since you are running directly off a battery (clean power) but I would install a .01uF capacitor on the output (and optionally an additional 100uF on the output)

Check your connection to the USB jack, make sure the polarity is correct. Many electronic devices have a reverse biased diode across their voltage input to prevent damage when reversed power is applied (this will effectively short out the power supply).

http://www.networktechinc.com/technote.html

http://www.eidusa.com/Electronics_Voltage_Regulator.htm
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Alan
Site Admin


Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB
PostPosted: Tue Apr 04, 2006 11:13 pm    Post subject: Re: "Help" section Reply with quote
jaredharley wrote:
I think the electronics needs a "Help" section for those looking for assistance on their projects.

I, for example, am working on this 9 volt USB charger that was featured in Popular Science. Using both the article and his website, I put everything together. An even 5 volts flows into the USB port, but as soon as I plug in a device, the "on" LED indicator turns off and no power flows to the device. I have no clue what's wrong - any ideas?[/url]


Bumped into this today. This is what you need (the large filter cap could be left out since you are using a battery though)

http://www.instructables.com/ex/i/9A2B899A157310299AD7001143E7E506/?ALLSTEPS
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB
PostPosted: Sat Apr 22, 2006 2:58 pm    Post subject: Re: "Help" section Reply with quote
jaredharley wrote:
I think the electronics needs a "Help" section for those looking for assistance on their projects.


I agree, we have a help section in electronics now Smile
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