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181  Using Arduino / Motors, Mechanics, and Power / Re: how use a step motor on: December 27, 2012, 08:22:44 am
Much has been posted on these forums about this stepper motor and driver. Do a search for '28YBJ-48'. - Scotty
182  Using Arduino / Project Guidance / Re: PWM control of many LED's from arduino on: December 25, 2012, 01:18:08 pm

Quote
1) use external chips;

Like this? https://www.sparkfun.com/products/10136

- Scotty
183  Using Arduino / General Electronics / Re: Mosfet data on: December 22, 2012, 12:47:43 pm
Thanks for all of your responses. Do I read it correctly from figure 3 that the mosfet doesn't reach full saturation or that 'saturation' is a ambiguous. Unlike the mosfet here http://www.sparkfun.com/datasheets/Components/General/RFP30N06LE.pdf. I can see saturation  clearly in figure 7. Also, do I read it correctly (in figure 7) that saturation can be attained with a gate voltage of 3v for a drain current of 20 amps but a higher gate charge is needed if a higher current is to be passed? - Scotty
184  Using Arduino / General Electronics / Mosfet data on: December 21, 2012, 08:33:42 am
I recollect from reading previous posts, warnings of confusing the Vgs value when the mofet starts to conduct value as the Vgs value to drive the mosfet to saturation. In this data sheet http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00003023.pdf, specifically what tables or charts would one find those two values? Thanks - Scotty
185  Using Arduino / Project Guidance / Re: Stand alone ATMega328p on: December 19, 2012, 03:07:33 pm
Thank You, Gentlemen, for your responses. I understand more clearly now and the info helps me in with deciding what path to take for a stand alone ATMega. What I plan to do is install the bootloader onto the 328s I have using an Arduino Uno. In the future I will most likely purchase 328s with the bootloader already installed. Since I want to be able to use the serial monitor for troubleshooting and since I already have a USB to serial adapter, I will include a header that will have Pin 1 = GND, Pin 2 = N.C., Pin 3 = VCC, Pin 4 = TX to RX, Pin 5 = RX to TX, Pin 6 = Reset.

Do I understand this right? FTDI uses TX & RX. ICSP uses Mosi, Miso & Sck. ICSP can install the bootloader and upload sketches. FTDI can load only sketches. FTDI only can be used for debugging through the serial monitor.

- Scotty
186  Using Arduino / Project Guidance / Stand alone ATMega328p on: December 19, 2012, 08:18:50 am
Have I got this straight?

1. The purpose of the bootloader is to facilitate ATMega328p communication with an IDE.

2. Assuming the bootloader is loaded on the ATMega328p, with an FTDI connector on a Stand alone ATMega328p, uploading and  troubleshooting (using Serial.print) would be possible via a USB to serial adapter board.

- Scotty
187  Using Arduino / Programming Questions / Re: Chicken Coop - LCD + 2 Fans + 2 Lights + RTC + DHT11 + Stepper on: December 09, 2012, 07:41:38 am
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This issue seem to be above your level of competency.
R i i i i i i g h t! - Scotty
188  Using Arduino / Motors, Mechanics, and Power / Re: Rail to move a camera at precise speed? (0.25 meters per second at 1mm accuracy) on: November 30, 2012, 10:24:38 am
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I can do this!  I can send you a picture of the slider.  The coding is easy.  After you see what I've built, you can tell me how much this setup is worth to you.

I'm interested in what you have done. Would you post pictures please? - Scotty
189  Using Arduino / Motors, Mechanics, and Power / Re: DC motor with very high torque on: November 30, 2012, 10:16:13 am
100kg. Is that correct? - Scotty
190  Using Arduino / Programming Questions / Re: second tcrt5000 reflective sensor will not trigger reverse relay. on: November 30, 2012, 08:31:38 am
Ouch! Won't this have the potential to be a dead short if both sensors detect a reflective media at the same time thus energizing both the forward and reverse relays at the same time? I think some code is needed to prevent that scenario. Also, relays are mechanical and are not instantaneous. One relay will be slower than the other to operate; therefore one may still have it's contacts closed (although the coil is no longer energized) when the other relay closes it's contacts , i.e., same same dead short scenario. Some delay is needed to ensure the previously energized relay has opened it's contacts before energizing the other relay.

- Scotty
191  Using Arduino / Project Guidance / Re: Solenoid & Stepper Motor power problem. PROTECT ME! on: November 29, 2012, 04:38:10 pm
I wouldn't call it a power loss; that suggests not having enough power. It would be a power waste in that the differential between input an output of a regulator is burned off as heat. e.g. for the 7812 the input is 19, the output 12 so 7 volts is 'burned off'. How much power is wasted can be determined by multiplying the voltage differential by the current going through the device. If your not energizing the solenoid ALOT, I wouldn't worry about it unless your running off a battery or battery pack; and I doubt that since 19 v would be an uncommon battery voltage. Same with the 7805. With your circuit you are only powering two ICs and the logic voltage they use is only for signals. The other way to go about it is to use switching regulators but they are significantly costlier.

Using a voltage divider for power is pretty much a no-no. In order not to have significant current flowing through the divider when connected across a potential, you've got to use some pretty high resistances. When you go to power a device with the divider, one or the other of those resistances will be in series with that load. A good amount of the voltage you need for your device will be dropped across the resistor.

Keep in mind that the 78xx series of regulators are only good for about an amp. They both have big brothers available in a TO3 package good for about 3 amps.

- Scotty
192  Using Arduino / Project Guidance / Re: Solenoid & Stepper Motor power problem. PROTECT ME! on: November 29, 2012, 09:47:04 am
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Now if only someone could teach me how to power this contraption with only one power supply

Bit of a waste of power but:

19v-------7812 regulator
  |             |        |
  |             |        --------------------------7805 regulator
  |             |                                              |
  |             ---------- solenoid supply           ---------- logic supply
  |
  ----------- stepper motor supply

- Scotty
193  Using Arduino / Project Guidance / Re: Solenoid & Stepper Motor power problem. PROTECT ME! on: November 29, 2012, 08:01:07 am
Oops? Data sheet shows pin 9 of this device as Logic supply voltage and pin 4 as Supply voltage. It appears you have these swapped. - Scotty
194  Using Arduino / Programming Questions / Re: Help with RPM code on: November 28, 2012, 09:31:52 am
Found this:
Properties of Pins Configured as INPUT
Arduino (Atmega) pins default to inputs, so they don't need to be explicitly declared as inputs with pinMode(). Pins configured as inputs are said to be in a high-impedance state. One way of explaining this is that input pins make extremely small demands on the circuit that they are sampling, say equivalent to a series resistor of 100 megohm in front of the pin. This means that it takes very little current to move the input pin from one state to another, and can make the pins useful for such tasks as implementing a capacitive touch sensor, reading an LED as a photodiode, or reading an analog sensor with a scheme such as RCTime.

on the Arduino site under Learning/Foundations/Microcontrollers/Digital Pins.

- Scotty
195  Using Arduino / Programming Questions / Re: Help with RPM code on: November 28, 2012, 07:22:57 am
Why is a transistor needed? Couldn't the 10K resistor be in series with the photo-interrupter collector to 5V line and the emitter of the photo-interrupter tied to ground; the signal being read at the resistor-collector junction? - Scotty
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