I'm trying to power an Arduino Nano using the 5v input. I'm using a ULN2003 to drive a 12v LED strip. I want to use the same 12v power supply to power both the Nano and the LED's. (I'm using a ATX computer power supply for prototyping purposes). When putting 12v on the Nano it seems to work for a bit, but then I get a flashing power led and it stops working. I put a 7805 (pin 1 left pin) 12v input, (pin 2 middle) ground, and (pin 3 output) on my multimeter, and I'm reading 11v on the output. I thought maybe it was a faulty module, so I tried a second one, and got similar results.
Any suggestions why I'm not getting the 5v output I'm expecting?

Thanks for any help!!

 

I'm trying to power an Arduino Nano using the 5v input. I'm using a ULN2003 to drive a 12v LED strip. I want to use the same 12v power supply to power both the Nano and the LED's. (I'm using a ATX computer power supply for prototyping purposes). When putting 12v on the Nano it seems to work for a bit, but then I get a flashing power led and it stops working. I put a 7805 (pin 1 left pin) 12v input, (pin 2 middle) ground, and (pin 3 output) on my multimeter, and I'm reading 11v on the output. I thought maybe it was a faulty module, so I tried a second one, and got similar results.
Any suggestions why I'm not getting the 5v output I'm expecting?

Thanks for any help!!

Have you double checked the datasheet by the 7805 manufacturer? Are you sure it's properly oriented? Posts some pics and simple diagrams.

 

I'm trying to power an Arduino Nano using the 5v input. I'm using a ULN2003 to drive a 12v LED strip. I want to use the same 12v power supply to power both the Nano and the LED's. (I'm using a ATX computer power supply for prototyping purposes). When putting 12v on the Nano it seems to work for a bit, but then I get a flashing power led and it stops working. I put a 7805 (pin 1 left pin) 12v input, (pin 2 middle) ground, and (pin 3 output) on my multimeter, and I'm reading 11v on the output. I thought maybe it was a faulty module, so I tried a second one, and got similar results.
Any suggestions why I'm not getting the 5v output I'm expecting?

Thanks for any help!!

It didn't happen without a schematic. Please post on in png format.

 

The 7805 requires a load. Do you have one?

 

You probably don't have enough of a load. The datasheet only specs the voltage regulation down to an output current of 5 mA. Try putting a 1 kΩ resistor between the output and ground and see what happens.

 

The 7805 requires a load. Do you have one?

While the datasheet doesn't spec the performance below 5 mA, there is no minimum output current given in the recommended operating conditions, which I think strongly implies that there is no load that is actually required. Still, if you run it below 5 mA you have no ground to stand on if it fails to regulate, even though it is reasonable to expect it to regulate well below that 5 mA level. But asking it to regulate with only half a microamp of load current (a 10 MΩ voltmeter input) is quite possibly asking a bit much. So putting a small load on the output is the low hanging fruit at this point.

 

If you just need 5V then get yourself one of those USB wall chargers. If you really need 5V from say a 12V battery then buy a usb charger for a car. Your psu will run cooler and you will be able to move on with your project.

 

If you just need 5V then get yourself one of those USB wall chargers. If you really need 5V from say a 12V battery then buy a usb charger for a car. Your psu will run cooler and you will be able to move on with your project.

If you just need 5V then get yourself one of those USB wall chargers. If you really need 5V from say a 12V battery then buy a usb charger for a car. Your psu will run cooler and you will be able to move on with your project.

Ok...to answer all questions...I think....
I put a 1K ohm resistor between ground and output....no difference...still outputti g 10.96v. Im using a 12v power supply to power a strip of LED's. I don't want to have two separate power supplies (one for lights, one for arduino). I want to regulate the 12v supply down to 5v without a second supply. I'll try to post a pic..

 

A usb car charger is a regulator just like the 7805 (except the 7805 is a linear regulator and the usb charger a buck regulator). You can open the case and remove it if you don't want the case. You can also get something like this:

http://www.ebay.com/itm/1-8-5V-To-3...8c4d6889efd2701422bb46&pid=100505&rk=1&rkt=1&

 

 

Ok...to answer all questions...I think....
I put a 1K ohm resistor between ground and output....no difference...still outputti g 10.96v. Im using a 12v power supply to power a strip of LED's. I don't want to have two separate power supplies (one for lights, one for arduino). I want to regulate the 12v supply down to 5v without a second supply. I'll try to post a pic..

Is the 7805 hot? Have you touched it with your finger?

 

 

In the first picture, it should show the red wire as the 12v input, the blue wire ground, and the yellow wire as output. I've put the 1K ohm resistor between ground and output. When putting my multimeter on it, still shows output of 10.96v.

The second picture is close up of the module...not sure it that is helpful or not!

 

I haven't tried touching it...I will try right away and let you know! If you don't hear back, you know it's really hot!! lol

 

Those are pictures. It is not a schematic. Pictures are very hard to see how you have things wired. Please post a schematic.

 

Not sure how long it should take to get hot, but it doesn't feel warm at all....

 

Where did you get said 7805s? If you got them from eBay there is a chance they are not 7805s at all. They could simply be resistors or pretty much anything else.

 

Not sure how long it should take to get hot, but it doesn't feel warm at all....

It should be at least warm. You are dropping 7V.

 

Those are pictures. It is not a schematic. Pictures are very hard to see how you have things wired. Please post a schematic.

I don't have the 7805 wired to anything yet. There is no schematic, as there is no circuit yet. Just 12v into the 7805. I'm hoping to put the 7805 between a power supply and an Arduino Nano, to power it with the 5v from the 7805. The rest of the 12v will be going to the led strip.
Sorry, I'm not sure what I could give you in terms of a schematic...

 

And you are measuring the voltage across the load resistor?