USB Boarduino - Quick Question

[Demonhawk]

I recently purchased a USB boarduino and I am planning on using it for an OBDuino project

Code: Select all

http://code.google.com/p/opengauge/wiki/OBDuinoDiagram

. This is my first duino and my first hardware related project so I'm a bit of a noob.My question is in reference to powering the USB boarduino. I know on the DC version it is labled as 5v GND, Vin; but on the USB version it is labeled 5v, GND, 3v. I was wondering is the voltage required to be 3v input, or am I able to use a voltage of 5v input on the 3v pin.

Any information would be great.

Thanks.

[unwiredben]

When you use USB, it's powered by the +5V line from the USB cable. The FTDI chip converts that to +3.3V and that's what's supplied to the +3.3V line. That voltage isn't used elsewhere on the board, AFAIK.

[Demonhawk]

What I mean is how would I go about powering it without using usb such as the vIN on the DC version.

[jamesm]

The Vin on the DC version goes through the regulator, so you can supply anything from 7V-17V and get the 5V that the microcontroller uses.

I don't have either version, but it looks like the USB version gets it's power from the USB connector, and doesn't have a voltage regulator. That means you need to supply 5V to the board if you're not connected to USB.

You need something like the Adjustable breadboard power supply to give you 5V:
http://www.adafruit.com/index.php?main_ ... cts_id=184

[Demonhawk]

I have a 5 volt regulator that i'm planning on using. But on my board where it would normally say vIN, it says 3v and I was wondering if it would be safe to supply that line with 5 volts

[jamesm]

I don't think so. The 3v is an output voltage from the USB -> Serial chip. If you have devices that use 3v, it's conveniently supplied for you, but you probably won't need it.

The 3v pin on the USB boarduino is in the same spot as the Vin pin on the DC boarduino, but they do very different things.

Just wire your 5v from the regulator to the 5v pin and it should work fine.

[Demonhawk]

So now I'm slightly confused. On my board it is 5V, Ground, 3v. I thought that the 5v was an output. Is it in fact an input and the 3v is the output?

[jamesm]

Like i said, I don't have one of these boards, so I'm going on what I can find on the website.

Take a look at the schematic: http://www.ladyada.net/media/boarduino/ ... inosch.png

There's a jumper labeled PWR between the 5v pin and VCC. If that jumper is attached, then the 5v pin and VCC are connected.

In that case, you can think of the 5v pin as a just a piece of wire. It's not an input or output, it's just wire connected to VCC. You can attach a power supply to that pin, and everything will work because the wire will have power. If the wire gets it's power from USB, it's still just a wire with power.

Does that make sense? I suggest you just try connecting your 5v power supply to the 5v pin and see if it works.

[jamesm]

I misunderstood something on the schematic.

The 5v pin is on JP4, and is labeled VCC, so the PWR jumper has nothing to do with it.

Still, think of the 5v pin as a wire connecting to everything else labeled VCC on the schematic. If you put power there, everything will work.

[Demonhawk]

I thought the 5v pin was an output pin. I'm just confused as to what pin I would hook up voltage in. What I'm really confused about can be seen on the picture of the board On the USB version it is 5v, gnd, 3v. On the other versions and other arduino's it is labeled 5v, gnd, vin. Which is why I'm wondering if the 3v is the vin and if it can only accept 3v or if I can use 5v.

[unwiredben]

Demonhawk, look at the schematic at http://www.ladyada.net/media/boarduino/ ... inosch.png

Line 1 of the USB connector (which carries +5V from the computer) goes to a jumper labeled PWR. If that jumper is set, it gets connected to the VCC signal. If you're not connecting a USB cable, you can leave the jumper off and connect +5V to any pin labeled VCC, and ground to any pin labeled GND. Leaving the jumper connects your +5V source to the USB port, which is OK as long as you don't plug anything into the port.

Pin 17 of the FT232R chip is labeled 3V3OUT. It goes to a pin on JP4. You don't need to connect 3.3V to this pin; it's just an output if you need to run 3.3V parts, and the power is supplied from the FTDI chip.

[seanrz]

i realise this is an old post but i have a question regarding the following: "Leaving the jumper connects your +5V source to the USB port, which is OK as long as you don't plug anything into the port." If I were to leave that jumper plugged in by mistake, could it fry my computer's usb port?

i bought one of the USB Boarduinos, brought it home, and plugged it right in to my computer's usb port to test it with the "blink" sample program. in about 5 seconds it was scalding hot. i unplugged it immediately, but my computer's usb ports no longer work. needless to say, i'm EXTREMELY frustrated and would appreciate any insight.

thoughts?

[unwiredben]

I was talking about what would happen if you powered the Boarduino from an external power supply. If you do that, you want the jumper removed so you don't connect the external power to your computer's VCC line.

The board getting hot and frying your USB port sounds like a short in your soldering to me. USB ports on computers should have protection circuity to keep that from killing the system, but the protection might take out the port to keep the rest of your computer safe.

[seanrz]

Thank you for your helpful reply.

sounds like a short in your soldering to me.

I kind of wish I'd soldered the components myself; I'd have no-one else to blame but myself. however, I purchased it preassembled. I guess I just got unlucky.

[seanrz]

You were right. On close inspection of the ftdi chip, pins 17 (3V3OUT) to 18 (GROUND) were bridge soldered. it appeared to be a messy connection and probably unintentional.

I broke the connection, and it works.