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 1 Using Arduino / Sensors / Re: Decoding thermistor characteristics table on: January 29, 2011, 10:39:50 pm Granted TC are not as cheap as a NTC but, you don't need a \$20 AD582 to used a TC either. Just a little thinking out of the box . But, that's another post.
 2 Using Arduino / Sensors / Re: Decoding thermistor characteristics table on: January 29, 2011, 09:56:23 pm Thermistors are odd devices and its not a trivial task to get a precise temp reading with them. I've used them in the past for trip point applications. Anyways, you will need to use the Steinhart-Hart equation to calculate the temp. Have a look at this site: http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Sensors/TempR.html    I would use a thermocouple.
 3 Forum 2005-2010 (read only) / Development / Re: Voltage regulator needed? Or not? Portable LED PWM on: January 19, 2011, 08:42:59 pm All depends the the cells or batteries that are used. If you use a single cell and the Vf of the LEDs are 3 - 3.4v that's not going to work, you'll need a boost Reg. I would start with the easiest solution, maybe four AA's, resistors and MoFETS,  see what that gets ya. It will give you an idea of what the next step will be.
 4 Forum 2005-2010 (read only) / Development / Re: Voltage regulator needed? Or not? Portable LED PWM on: January 19, 2011, 09:02:37 am A lithium cell be a good choice. They have an excellent energy to weight ratio. Charging them safely maybe an issue. Lithium needs to be charged with a constant current/ constant voltage charger. constant current @ 1/3 C rate until the cell voltage reaches 4.2 volts and switch to constant voltage mode of ~ 4.5 volts to top off the cell About  20% of the energy in the topoff. Anything above 4.5volts and the cell may explode.  So, the voltage needs to be controlled.  I did a white LED drive that used a single lithium cell a few years ago. I used two of these: http:// http://www.maxim-ic.com/datasheet/index.mvp/id/3025 and a buck/boost 5 volt regulator for the power supply. The regulator was programmed to shut off when the cell voltage dropped below 2.5 volts. Lithium doesn't like a deep discharge. PWM of the EN pin on the MAX1916, to control brightness, was done on an AVR.
 5 Forum 2005-2010 (read only) / Development / Re: Help Newbie Project on: January 19, 2011, 09:55:29 am First, you need to know what type of tag you will be reading. There are several different types that work on different frequencies. Then look here:http://www.sparkfun.com/categories/144 and see if any of the readers are compatible. Looks like most of these readers spit out a serial stream, be it USB or 232.  Use the Arduino to parse the data.
 6 Forum 2005-2010 (read only) / Development / Re: Help Newbie Project on: January 18, 2011, 01:54:56 pm What type of "data" are you trying to acquire .....analog? ...... digital?.... What type of RFID?near field? We need more info...much  more
 7 Forum 2005-2010 (read only) / Development / Re: Pellet stove controlelr. on: January 17, 2011, 03:10:25 pm Wissy, you may want to look at a cheap PLC to get your prototype up and going. PLC would make the hardware interface easer.
 8 Forum 2005-2010 (read only) / Development / Any interest in a 802.11 Shield for a Mega2560 ? on: January 17, 2011, 12:41:00 pm Just putting out some feelers. Besides my full time design job, I also do contract design. I have just finished a PCB based on the ConnectOne - Wi2Wi. chipset for 802.11 communications. At my "real" job, I use Arduino for rapid prototyping and one offs. Anyways, I'm going to need 802.11 solution for a Ardino project. It will be interfaced to a Mega2560, so I thought I would reuse the design and change the form factor to a "shield".I have attached a pic of one the prototype PCB's just for a look see. The prototype is nothing more than ConnectOne's Secure Socket iWiFi with a PS and interface logic added. http://www.connectone.com/products.asp?did=73&pid=61Pic: The shield would be an interface for the module from ConnectOne and include:Mega2560 form factor3.3Volt power supply (maybe a 5.0V for the Mega)3.3 to 5.0 volt level shifting for communication.Headers for the Secure Socket iWiFi. (you buy your own from Mouser, ~\$50RS232 port for configuring the ConnectOne part off of the Mega via ConnectOne's tool. Pass through headers for stacking the Mega2560.various LED's and switches   Any interest? If so, we'll work out the details later.Thanks,John
 9 Forum 2005-2010 (read only) / Development / Re: (updated) building a circuit - can you look at it? on: January 17, 2011, 11:05:16 am At a glance, I would add gnd connections to your connector(s) to the other devices (serial). Add a few 0.1uF caps on the power - gnd of the connectors also. I would move the diode to the input of your 7805.
 10 Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Dealing with DC Motor Stall Current on: January 21, 2011, 01:00:52 pm If you are still having an issue with inrush, try a power NTC thermistor.
 11 Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Dealing with DC Motor Stall Current on: January 18, 2011, 04:25:24 pm I think you need to implement a "soft" start as  Lefty suggested. What I have done in the past is kinda a dual PWM. Sorta like FM modulation if you will. During the ON time, PWM at a high frequency. Hope that was clear.
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