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181  Forum 2005-2010 (read only) / Troubleshooting / Re: Using the tx rx pins on Arduino Duemilanove on: February 07, 2009, 11:08:42 pm
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Any chance I could have fried the vdip2 if I tried to use RS232 serial on it?  Geeze, I hope not.  :'(

Yeah, that definitely could fry something. RS232 could be 15-30V and swings AC. Needless to say a TTL (rated 0 to 5v) device is not rated to have 30V negative on an input pin. Nor is it rated to have 30V positive on a pin. Your RS232 serial might only have been 15V but that's still three times the rated voltage of a 5V TTL device.
182  Forum 2005-2010 (read only) / Troubleshooting / Re: Cannot Upload to Freeduino on: January 01, 2009, 10:05:36 pm
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I am seriously considering just adopting a no-bootloader environment and just using an ISP instead of buying another Arduino if I can't get this thing to work.

Well, if you have a working parallel programmer then there is certainly no harm in doing it that way. In fact, it saves you the flash space that the bootloader would have taken up.
183  Forum 2005-2010 (read only) / Troubleshooting / Re: Arduino Diecimila not loading sketch!! on: January 01, 2009, 07:43:01 pm
Well, unfortunately it seems like you've probably smoked the board somewhere. The computer will register a connection if the FTDI chip on the arduino is still working (at least for the most part.)

The black chip you are referring to would probably be the 7805 voltage regulator and you board would probably be the diecimila board. That chip is supposed to get somewhat warm but if it got really warm then it means that there was a large current draw on the board. This could be due to a short circuit somewhere or maybe something you had plugged into the board.

A number of bad things might have occurred. If the atmel 168 chip got too low a voltage then it's flash could have gotten corrupted. If the bootloader is corrupted then you won't be able to use the USB interface to upload sketches. You can use a parallel port programmer to do it. Chances are, you don't have one of those. You also could have some other component which is bad.

Depending on how seriously you are into this (as a hobby, a job, a very serious hobby, etc) you really should invest in spare parts. Get some 7805's, some spare caps, resistors. You really also ought to order up more atmel 168 processors. It's best for the hobbyist to order chips already programmed with the bootloader so that you don't have to get special stuff to do it yourself. Though, a programmer can be used to reload the bootloader onto chips you've gotten corrupted so if you are dealing with a number of arduinos then it might be worth it.

In short, I think that you are going to have to assume that your board is damaged in some way.
184  Forum 2005-2010 (read only) / Troubleshooting / Re: Arduino Diecimila not loading sketch!! on: December 31, 2008, 10:09:30 pm
It means that something is not working with the link between the arduino and the computer. It could be a lot of things.

How are you sending to the arduino? Usb? FTDI cable?

Is anything else hooked up to digital pins 0 and 1?

Do you have to push the reset button on your type of arduino like board in order to get it to accept a new sketch? ( you do have to do that on some models)

Are you sure you are sending to the right serial port?

Is there something wrong with your cable?

You see.... lots of questions. You need to be extremely specific about your setup and what you've tried in order for people to help you narrow this down. This can be a really annoying problem.
185  Forum 2005-2010 (read only) / Troubleshooting / Re: Fried Arduino BT question on: December 31, 2008, 12:16:40 pm
You could unsolder that and replace it with a new chip. It won't be easy as it's a surface mount chip with very small pins. However, you need to be thorough in checking the other components on the board. It's not certain that the chip in question is the only bad part.

I don't have a BT arduino and I can't see any of the lettering on that chip so I couldn't tell you what it is.
186  Forum 2005-2010 (read only) / Development / Re: Max 232 And arduino/ sanguino schematics on: October 03, 2009, 05:41:42 pm
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Note that this is not a "connection" from VCC to GND; it's a CAPACITOR between VCC and GND.

Oops... Yes, sorry for using such poor terminology.
187  Forum 2005-2010 (read only) / Development / Re: Max 232 And arduino/ sanguino schematics on: October 02, 2009, 09:03:15 pm
Oh, and you asked why a connection from VCC to ground is needed. It's for noise suppression. Digital ICs tend to be noisy and they also tend to send some of that noise back through their power input. With lots of ICs all in the same circuit they can and will send interference to each other. This interference will do strange and hard to diagnose things to the functioning of the circuit. You do not want this at all. This is where our friend the decoupling capacitor comes in. It suppresses the noise on the power pin. In short, use them. You will thank yourself later.
188  Forum 2005-2010 (read only) / Development / Re: Max 232 And arduino/ sanguino schematics on: October 02, 2009, 08:52:35 pm
Westfw's schematic is pretty much how you'd want to hook it up. Except that the schematic uses both of the recieve and transmit lines of the max232. You don't need to do that if all you want is one serial line. The max232 supports two complete serial lines. You just use R1 and T1. On a 9 pin serial line that's pins 2 and 3 (with 5 being the ground.) For simple RS232 serial those are the only three pins that need to be hooked up. This means that in this schematic you'd be using T2 and R1 which is confusing but won't hurt anything.

So if you want one TTL to serial connection then follow that schematic but don't hook up the connections to the DB9 pins 4 and 6.
189  Forum 2005-2010 (read only) / Development / Re: Modify Diecimila to run at 3.3v? on: February 12, 2009, 08:32:28 pm
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What about when plugged into the USB?  isn't that a 5V source?

Yes, USB is 5V so if you want to power a 3.3V board off of it you'd need to use a regulator or a voltage divider.
190  Forum 2005-2010 (read only) / Development / Re: Modify Diecimila to run at 3.3v? on: February 12, 2009, 10:02:21 am
The actual ATMEGA168 chip can easily run at 3.3V but not at 16Mhz. So, the solution is to replace the 16Mhz oscillator with something slower. The chip can run at 1Mhz with it's built in timing circuit (or 128KHz if you want). If that's too slow you might be able to get something else. You really have to look at the Mega168 spec sheet and find a Mhz rating that is fast enough for your needs but will run at 3.3V.

Keep in mind that if you change the Mhz you will also change all of the timings of things. Serial communications will become problematic very easily. I don't know how well the arduino delay functions will work.

I suppose I'd need more information about what you are trying to do  and how fast you need the chip to run to be able to say much of anything concrete.
191  Forum 2005-2010 (read only) / Development / Re: Using diodes to drop voltage on: January 23, 2009, 07:08:20 pm
Yeah, I've had to buy power resistors before (you'd think that industrial workers would be able to understand the concept of a 30% duty cycle on a welder but NOOOOOOO) and I don't really want to do that for this application. For right now I'll hook up an LM317 to get the prototype up and running and in the future I will almost certainly use some form of buck converter to get the voltage down to the proper level.
192  Forum 2005-2010 (read only) / Development / Re: Using diodes to drop voltage on: January 23, 2009, 03:03:39 pm
The TO-220 form factor regulator is from TI. And that was the $15 part I was referring to that Digikey had.

I did order up one of those convertors from Sure electronics. We'll see how I like it.

Thanks everyone.
193  Forum 2005-2010 (read only) / Development / Re: Using diodes to drop voltage on: January 23, 2009, 01:45:23 pm
Yeah, I do think that in the long run a DC-DC convertor will be the best option. I plan to make more than one of these units so I'll likely go with some sort of buck switching reg for the rest of them. I'll probably just use the LM317 for the initial prototype though, just to get something working. China is a long ways away and if I wait I'll be sitting here for two-three weeks.
194  Forum 2005-2010 (read only) / Development / Re: Using diodes to drop voltage on: January 23, 2009, 12:49:46 pm
In small quantities the DC-DC convertor is actually around $15 from digikey but I could search around for a better price. I've already got LM317's, heat sinks, and thermal grease laying around so that's the more expidient option. However, it also wastes about 57% of used energy as heat. The DC-DC convertor is about 90% efficient instead of 43% efficient. Like you said, the LM317 and heatsink is cheap. I probably really don't have more than $2-3 into the linear parts to do one unit. Choices, choices...
195  Forum 2005-2010 (read only) / Development / Re: Using diodes to drop voltage on: January 23, 2009, 12:28:32 pm
Yeah, I know about DC-DC convertors. I could do that, it's just a little more money. Maybe it's worth it though.

I'm planning on drawing maybe 0.5A. This is still way more than 1W heat dissipation (at 13V the drop to 5.6 is 7.4V times a half amp is 3.7W heat dissipation)

It makes sense what you said about heat dissipation in diodes. I'm still in the learning phase and I just couldn't get my head around it. But what you said makes sense.

So the first diode (in my original idea) would see 13V at one end and 12.4V at the other for a total drop of 0.6V. 0.6V * 0.5A is 0.3W. So the best diodes could do is to spread the heat dissipation out among more components. And thus all I could hope to do is increase the cost but not the efficiency. This makes sense now that I really think about it.

I don't mind using a heatsink. Now I just have to determine whether it's worth it to use a linear reg with a heatsink or spring for a DC-DC conversion circuit to get higher efficiency.
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