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31  Using Arduino / Project Guidance / Re: Power Supply on: February 08, 2013, 12:37:48 am
The AMS1117 had max voltage of only 10V, your 9V power adapter may output higher then 10V.
I have a different datasheet that says the max Vin is 15V. Mine is from AMS and yours is from "HotChip". Hahaha. Which is correct? Who knows.
32  Using Arduino / Project Guidance / Re: Power Supply on: February 07, 2013, 07:26:54 pm
Yep. You can't even buy the regulators for that little. I guess I am glad I didn't order that model. I was actually just looking at those a couple weeks ago, but decided to buy mine from nkcelectronics instead which is 3.3/5V independently selectable for each rail (no on/off switch built in, though.) I like it.
Its a nice little board. Seems to have been designed for the MB102 breadboard even though its description doesn't say so. Its probably priced right since it comes assembled, but watch out for the shipping cost. Start a blog and let us know how it works out.
33  Using Arduino / Project Guidance / Re: Power Supply on: February 07, 2013, 05:00:08 pm
If your 5V regulator is not burned up, it is damaged. You can see a burn mark on it in your picture. If it is working, it won't be soon. The fact that you have 3.3V selected and it is the 5V reg taking the hit would suggest it is something on the input to the 5V regulator (too high of a voltage) or a short after that. Connected to the 5V line are the LED, C2, C3, and the 3.3V regulator. I doubt the LED would blow it even if it shorted out since R1 would still limit current. C2 may be a crappy cap and shorted internally, or perhaps there is solder shorting out under C3. Finally, the 3.3v regulator may be shorted from Vin to GND. Unless they are using counterfit regulators, I would be surprised if the regulator is defective. I suspect the cap, C2. You could desolder it and see if things work with it removed. It is just a filtering cap and won't break the circuit with it removed (but might make the supply noisey.)
I removed Cap C2. There was no change. I know that the Vout of the 5v regulator goes to Vin of the 3.3 v regulator. From either of those points to ground shows a 180 ohm resistance.

Perhaps the point is that the whole thing cost about $2.50. It might be best to just scavenge the parts and build your own. It would be nice to stop the thing from being bought altogether or communicate the problem to the designers. Both seem impossible at this point.
34  Using Arduino / Project Guidance / Re: Power Supply on: February 06, 2013, 05:41:37 pm
Hi again!

Thank you for answering my question in the first place smiley-grin.  I have selected the voltage ( 5v ), please refer to the attachment.
There is still no power being supplied to the bread board... and the AMS1117 chips is smoking smiley-eek-blue  Is the chips being defective or its me..? the power being supplied to the Bread Board power module is from a 220VAC to 9VDC transformer.  Any help will be appreciated!  Thanks in advance! smiley-lol

Your board is defective! I received one a few weeks ago and the AMS1117-5 regulator gets hot within seconds of plugging in the barrel connector. The power adapter is the same one I use for my Arduino UNO board, so its not an input voltage problem. My tests show that there is about 185 ohms between the 5 V output and ground. But all the other connections seem to be intact. I expect its a problem within the printed circuit board layers and so it cannot be fixed.

This power module is ubiquitous - and sold by many different sellers. Keep in mind that today is Feb 6, 2013 and these defective units are still shipping. Sindya (one of many sellers on Ebay) offered gave me a partial refund. I won't buy anymore from anyone though; almost all models and versions have the same regulator chips and the same layout, and likely the same problem. I just don't know why its never been reported before. I have attached a schematic for the version that you have (and that I have). The vendor asked that I send them a manual if I find one - HAHAHAHA. Hope you have good luck. I plan to build my own.

The final joke is the USB connector. Its supposed to be a male, not a female (you're left with a female end when you connect an extension to the computer). If you have an adapter and connect it to your computer, you may find that the board uses neither the 5V nor 3.3V regulator. I just can't tell from the schematic.
35  Using Arduino / General Electronics / Re: New YwRobot MB102 power module overheats on: February 05, 2013, 04:50:52 pm
So what "power adapter plug" - what polarity, what voltage? - and is there a manual / datasheet for this module?  
Is the polarity of the barrel jack socket marked / indicated (believe it or not these things are not standardised).
It does sound like a short circuit at the 5V side of things - do you have a multimeter?
There is no manual or datasheet for the product and no other info. Its from China; need I say more?
The adapter is an over the counter unit with an nominal output of 9 VDC at 800ma. The open circuit voltage is 13.5 V. I use the same adapter as the supply for the Arduino UNO board. The interior of the barrel is positive.
The 5v regulator is designated as ASM1117-5 whose datasheet I have attached.
I have followed the circuit on the schematic from the input adapter plug. The socket's center goes to the 1117-5 input pin 3; pin 1 is connected to ground and pin 2 is (at least) connected to the green LED. For a green LED voltage drop is typically 2.2v. So for a 5V supply the current through the resistor is (5-2.2)/470 = ~ 6 mA. So it must be something else.

I've traced through the rest of the connections and they all appear to be OK, but there is about 180 ohms between the 5V rail (1117-5 pin 2) to ground as measured with an ohmmeter. Reversing meter leads produces the same results. I can't think of what might cause that, but it would draw only 27 mA from the regulator whose max current is ~1 A.

There is no similar resistance between the 1117-3 regulator output and ground. Removing jumpers does not eliminate the 5V, 180 ohm shunt, nor does changing the DPDT switch.
36  Using Arduino / General Electronics / Re: New YwRobot MB102 power module overheats on: February 05, 2013, 12:20:37 pm
Can you post a link to the datasheet or info on this module?  Can you explain exactly how you are testing it?
I have attached a photo and what I think is the schematic for this version of the board. That's all I have.
To test it, all I did was to insert the power adapter plug into the black socket on the board. I did not connect anything to the supplies, and in fact jumpered both sources to an off position. The 5 v regulator heats to untouchable in 2-3 seconds.
37  Using Arduino / General Electronics / New YwRobot MB102 power module overheats on: February 04, 2013, 07:19:14 pm
I purchased a YWRobot M102B Power Module, and received it only a few days ago. While testing it, I immediately learned that the 5V regulator is, within seconds, too hot to touch. And this was without any load whatsoever. I used the same power adapter as I use for the Arduino UNO whose 5v regulator doesn't get hot at all. I assume then that the module must have some wiring error in it - such that a strong load is created. As the PCB is multi-layer, I doubt that I'll be able to fix the problem. Any suggestions - outside of returning it or discarding it?

Note: The USB connector is female and, of course it should have had a male connector.
The UNO regulator (ON 117-5) and that of the power module (ASM-1117-5) appear to be the same although different brands. The Max input voltage is 15 V, and the power adapter is under that.
38  Using Arduino / Networking, Protocols, and Devices / Re: UNO I2C clock stops unexpectedly. on: January 19, 2013, 01:28:23 pm
For the life of me, I can't download the PDF in the original post. I get error 503 from the web site when I click it. Could you post a link to this device?
The URL for product info is at: There is a link to the user manual, but the schematic has to be requested via the sales email address. I also get the 503 error when I try to download it. Perhaps its been deemed to be proprietary.

How often will communications be required? I heard a story once about an I2C device that was overloaded by too-frequent bus communication and it affected its internal operation as a result.
This is no longer the problem. Ignore the code in my first post.

Here is the current problem:
The module is sent a count that sets an oscillator frequency. That frequency is determined by the high 14 bits of an unsigned word. The two MSB enable or disable the two clock outputs. The SDA and SCL lines have 4.7K pull-ups, and the waveforms look good on the scope.
The current program sends one oscillator value at setup time. Nothing is sent in the "loop()". The problem now seems that higher values don't get to the module. I have to power down the module and the UNO and then power up the UNO and the module in that order. Once the module powers up, the output goes to the set frequency.

Is 0x2E the write address? Then 0x2F would typically be the read address. The read/write bit is the least significant bit with zero indicating write and one for read. Shifting the address by one bit ( >>1) seems unusual, but without knowing anything about the device or seeing the datasheet, I can't be certain.
This is the technique needed by the Wire library.
39  Using Arduino / Networking, Protocols, and Devices / Re: UNO I2C clock stops unexpectedly. on: January 18, 2013, 11:24:03 am
I can no longer reproduce the problem. It may well have been a loose wire on the breadboard. I never seem to have any luck with hardware.
But the module is still not working. I just need to look at it to describe the problem.

@Crossroads: "I2C devices have to reply with an ACK bit as part of the tranfer. Is the device responding?"
Yours was a puzzling comment. The program is in a loop of writes. Why would an ACK stop everything? OR are you saysing that at some point, the WIRE library hung because it missed an ACK?

@ robtillaart "x = uint8_t TwoWire::endTransmission(void)". That was REAL good to know. I will use it. Seems I should keep the library code handy.

@ Jack Christensen: "I was under the impression that the SCL line idles high once data transmission is complete." It does, but there is a write loop that continually sends an address.

Again...can't seem to reproduce it for now.
Thank you all.

40  Using Arduino / Networking, Protocols, and Devices / UNO I2C clock stops unexpectedly. on: January 17, 2013, 12:22:20 pm
I'm confused as to why the I2C clock from the UNO stops after some repetitions when the SCL line is connected to a device.
I'm using the following program:
#include <Wire.h>
//I2C-OSC Freqency setter
//I2C: A4 (SDA), A5 (SCL)
const byte I2C_Write =(0x2E >>1);// I2C write address =0x17
const byte x=0xFF;

void setup()
    Wire.begin();        // join i2c bus (address optional for master)
void loop ()
The interfaced device is an I2C-OSC module. I have attached a schematic for the module. It is fed with 5V and ground, SCL and SDA from the Arduino.
I don't understand why the loop of the programs produces a valid clock (SCL) for some few seconds and then stops (leaves the line high) altogether until the UNO is manually reset, after which the same thing happens.

Note that there is a normal repeated clock when the SCL wire to the module is disconnected and the UNO is reset.

PS: If I lengthen the delay, the SCL clock lasts longer, but still stops in a few seconds.
41  Using Arduino / General Electronics / Re: MS8 (8 bit MSOP) to DIP Adapter(s)? on: January 16, 2013, 03:09:12 pm
Yes, I saw those after I wrote the post. The large grey ones are too expensive, and the others require the MSOP chip to be soldered to the adapter board. That's not what I wanted because the soldering is hard for me to do. I wanted to bend the MSOP leads and insert them into a socket.
42  Using Arduino / General Electronics / MS8 (8 bit MSOP) to DIP Adapter(s)? on: January 16, 2013, 02:10:37 pm
I'm a hobbyist working on some personal projects. For one of them, I want to use the LTC6904 chip (
but it is only made in an 8-bit MSOP package (MS8). I don't wish to solder this chip (I'm just not good at it), so I was looking for an adapter to some carrier - like a DIP - that I could solder into a breadboard or insert into a solderless breadboard. After some time looking, I didn't find one. Perhaps someone knows of such an adapter?

PS: I was hoping to bend the pins in the IC downward and then insert them into a socket.
43  Topics / Robotics / Re: Angular position sensor? on: January 09, 2013, 02:10:35 pm
Seems to be a common problem, measuring angles, specially when it comes to making mobile robots. At the end I had to make my own board, now selling it..I have a few boards on my website ,
Very nice. I bookmarked the web page.
Thanks very much.
44  Using Arduino / Microcontrollers / Re: Uno External 5V direct connect? on: December 19, 2012, 07:47:08 pm
Alternatively you can bring the +5V into the headers directly, as that bypasses the onboard regulator too.  You could do that with a simple pair of male headers connecting to +5V and the adjacent GND, or put those on a small perfboard as a shield if you want to use a screw terminal or similar to secure your external power line.

Yes, I though of that, but then I would need to be sure to remove that 5V wire when I plug in the USB cable to program the micro. That seems a risky approach.
45  Using Arduino / Microcontrollers / Re: Uno External 5V direct connect? on: December 19, 2012, 07:44:51 pm
I have a Rev3 Uno. Is there a way of using a 5V external supply (from a 7805 regulator) to power the board?
I mean without modifying the board?

Well the way I do it is to get an old spare USB cable and lop off the PC end, separate out the ground and +5vdc wires and wire them to your external +5vdc voltage source. Then just plug it into the arduino's USB connector.


Hahaha, of easy solution. And then I would be sure to disconnect that USB cable with the one from the desktop when I want to program the micro. When programming the micro, would that create a problem between the 5V on the USB cable running the Uno, and the external regulator feeding other components.
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