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by Tage
Mon Dec 09, 2013 3:26 am
Forum: Automation, sensing and robotics
Topic: Low power MOSFET to Launch the Pi
Replies: 13
Views: 3970

Re: Low power MOSFET to Launch the Pi

I am no expert on very low power regulators, but would myself consider LTC3621 or some other similar switching regulator. I don't know how much current is needed, but this part can handle 1A and consumes only a few micro amperes at light load. There is a diversity of different partnumbers to choose ...
by Tage
Mon Dec 09, 2013 1:51 am
Forum: General discussion
Topic: Outdoor power
Replies: 22
Views: 7874

Re: Outdoor power

my gut feeling that a 60W solar panel is needed is based on the assumption that there will be about 2 hours of sunlight each day, but the panel will not be providing full power. then there will be weeks when the sun only shines perhaps one day, then the cloudy weather returns for another week. etc. ...
by Tage
Sun Dec 08, 2013 4:20 pm
Forum: General discussion
Topic: Outdoor power
Replies: 22
Views: 7874

Re: Outdoor power

my gut feeling is that you need about 60W panel and a 100Ah 12V deep discharge battery to run the Pi continuously year around.
by Tage
Sat Dec 07, 2013 11:37 pm
Forum: General discussion
Topic: Outdoor power
Replies: 22
Views: 7874

Re: Outdoor power

an alternative to increasing the solar panel size is to use two deep cycle batteries and exchange the battery with regular intervals for charging.
by Tage
Sat Dec 07, 2013 10:16 pm
Forum: General discussion
Topic: Outdoor power
Replies: 22
Views: 7874

Re: Outdoor power

you could use a solar panel to charge a 12V SLA battery, and power your Pi from that battery using a USB charger adapter. the problem is the cost of the solar panel and the fact that the Pi draws more power than the panel and battery can provide. So you need to keep the Pi shut off most of the time ...
by Tage
Sat Dec 07, 2013 4:01 pm
Forum: HATs and other add-ons
Topic: Power Supply
Replies: 24
Views: 14777

Re: Power Supply

I would like to comment on the discussion regarding if a power supply can be damaged or overheated by back feeding it from another supply. (my background is in power supply design.) It is definitely possible. that is one reason why it is not a good idea to use powered USB hubs that do not meet the U...
by Tage
Sat Dec 07, 2013 2:22 am
Forum: Automation, sensing and robotics
Topic: Low power MOSFET to Launch the Pi
Replies: 13
Views: 3970

Re: Low power MOSFET to Launch the Pi

Perhaps you can use a 12V sealed lead acid battery and get a car charger adapter of the type used to charge iPad. the 5.1V output could power the Pi and the Arduino. if you run the Arduino with 5V it is easy to control a p-channel MOSFET directly from a GPIO. if you need to communicate between the 5...
by Tage
Fri Dec 06, 2013 3:52 pm
Forum: Beginners
Topic: Beginner question
Replies: 13
Views: 1753

Re: Beginner question

We have gotten new breakout kit tonight. We finished setting up the RDP server. Tomorrow we will solder, I have to make sure that the solder does not run between point right? Sorry to ask such basic electronic questions, I have done many different hobbies some that included soldering but never such...
by Tage
Fri Dec 06, 2013 3:14 pm
Forum: Automation, sensing and robotics
Topic: Low power MOSFET to Launch the Pi
Replies: 13
Views: 3970

Re: Low power MOSFET to Launch the Pi

yes, the p-channel MOSFET is kind of backwards in the way that the voltage across drain to source is negative (and the body diode has the anode to drain and cathode to source, so it will conduct if you have the transistor the wrong way). and you have to apply a negative voltage to the gate, relative...
by Tage
Thu Dec 05, 2013 8:54 pm
Forum: Automation, sensing and robotics
Topic: Low power MOSFET to Launch the Pi
Replies: 13
Views: 3970

Re: Low power MOSFET to Launch the Pi

Draft2.png you can also use an n-channel MOSFET, but you will need a voltage that is higher than the Source to turn it on. if you have 12V available you could connect it in this way. then the gate-source voltage will be 12V-5V=7V when the npn is off. Note that in this circuit, your load will have 5...
by Tage
Thu Dec 05, 2013 3:39 pm
Forum: Automation, sensing and robotics
Topic: Low power MOSFET to Launch the Pi
Replies: 13
Views: 3970

Re: Low power MOSFET to Launch the Pi

Draft1.png you need a p-channel MOSFET and a small npn transistor. connect as shown. RLOAD is your Pi. the part numbers in the example are old. look for SOT-23 type p-channel MOSFET with 20V rating and Rdson at 4.5V gate voltage should be 0.1ohm or lower. for example DMP2123L. the npn transistor in...
by Tage
Tue Dec 03, 2013 8:16 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: High resolution Analog to Digital Converter [FOUND!]
Replies: 12
Views: 6344

Re: High resolution Analog to Digital Converter

check out the Linear website,
http://www.linear.com/products/analog-t ... _%28adc%29

for example, LTC2440 at around $7 each or $50 for the demo board.
by Tage
Tue Dec 03, 2013 8:09 pm
Forum: General discussion
Topic: Intersil power module on Pi?
Replies: 4
Views: 894

Re: Intersil power module on Pi?

in my opinion, this power module is not a good choice for the Pi. at 12V in and 5V out it has a really bad efficiency below 1A load. it may even be that it has lower efficiency than the series regulator you tested, at 0.5A. this module is more optimal for lower output voltages and higher current lev...
by Tage
Thu Nov 28, 2013 4:09 pm
Forum: Troubleshooting
Topic: reading a mosfet transistor datasheet
Replies: 5
Views: 959

Re: reading a mosfet transistor datasheet

Imagine that you are holding the transistor with the flat front face facing you and the pins pointing down. the Source is to the left. with knowing the Gate being the middle pin you could also measure which pin is Source by using a multimeter in diode mode. there is always a body diode that is part ...
by Tage
Thu Nov 28, 2013 4:40 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO Pin voltage
Replies: 2
Views: 493

Re: GPIO Pin voltage

depends on your point of reference
by Tage
Mon Nov 25, 2013 8:33 pm
Forum: Automation, sensing and robotics
Topic: Transistor - resistor calculation
Replies: 4
Views: 1952

Re: Transistor - resistor calculation

I'm tinkering with a stepper motor driven by an Easydriver controller and all is working well. By default the controller is set to 1/8 step but this can be overridden by tying a couple of the pins to ground to set 1/4, 1/2 or full step and I figure using a couple of transistors is the easiest way t...
by Tage
Sat Nov 23, 2013 3:50 pm
Forum: Other projects
Topic: Multi-Pi CarPC
Replies: 2
Views: 2561

Re: Multi-Pi CarPC

It is a very interesting project. I am looking forward to learning more. I am not a programmer but a power electronics guy and I have been thinking of implementing similar ideas for my motor home. How did you implement the connection over 3G? I assume the car will have to call the external server an...
by Tage
Tue Nov 19, 2013 3:17 pm
Forum: Advanced users
Topic: Cheap UPS?
Replies: 22
Views: 13787

Re: Cheap UPS?

Hello, I've had my Raspberry Pi for about a year now and I got it set up the way I want (basically). However, the last months I've had a few power outs which has screwed a bit with it. Once I had to reflash the SD card which was quite annoying. So I thought to get a UPS for the Pi. Now, it's really...
by Tage
Sun Nov 17, 2013 4:47 pm
Forum: General discussion
Topic: Power supply problems (too many amps)
Replies: 8
Views: 2391

Re: Power supply problems (too many amps)

I'm new to electrical so everyday I'm learning something new, I recently switched from using motor drivers to using transistors to controlling my motors and through this I think I've found a problem with my power supply. My power supply is 13.5v dc and 1.0 amp but when i put it through my transisto...
by Tage
Fri Nov 15, 2013 4:03 am
Forum: General discussion
Topic: Relay Question - Please Help
Replies: 9
Views: 1249

Re: Relay Question - Please Help

you should ask for a schematic of the relay board from the manufacturer. at least they should tell you how to use this board with you Pi. as they claim that it is possible... this seems to be yet another example of how low quality products are being sold on the internet by people that do not even ha...
by Tage
Wed Nov 06, 2013 2:22 am
Forum: Automation, sensing and robotics
Topic: Glasses for the blind
Replies: 5
Views: 2082

Re: Glasses for the blind

I am quite sure that there are laser range finders that are scanning so they cover a wide angle. I will ask because I may have the opportunity to talk to some guys involved in these products within the near future. regarding ultrasonic sensors, I would think there are ways to move the sensor without...
by Tage
Tue Nov 05, 2013 1:48 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO: Analog Input?
Replies: 16
Views: 100935

Re: GPIO: Analog Input?

you can read analog signals without using an external ADC if you use the method described in http://www.raspberrypi.org/phpBB3/viewtopic.php?f=29&t=21287&p=447537#p447537 this only works for relatively slow signals such as battery voltage or temperature. but it works, and you only need some type of ...
by Tage
Mon Nov 04, 2013 3:15 pm
Forum: Off topic discussion
Topic: Baby Monitor Interference from chargers?
Replies: 1
Views: 1595

Re: Baby Monitor Interference from chargers?

EMI noise can be tricky to figure out, but I would start the trouble shooting by trying each charger one at a time to find out if it is the charger that is noisy. The noise could be at any frequency, but my guess is that it is at hundreds of MHz so it is radiating using the wiring and charge cables ...
by Tage
Mon Nov 04, 2013 2:57 pm
Forum: Automation, sensing and robotics
Topic: Glasses for the blind
Replies: 5
Views: 2082

Re: Glasses for the blind

I would look into miniature laser range finders, and ask the manufacturers for a free sample to evaluate. The people that are building unmanned vehicles and flying objects also would know a lot about these different ways of detecting obstacles. Many cars these days are sensing objects all around the...
by Tage
Mon Nov 04, 2013 12:31 am
Forum: Automation, sensing and robotics
Topic: Quick help please: how to connect 12V PWM PC fan to Pi
Replies: 3
Views: 3716

Re: Quick help please: how to connect 12V PWM PC fan to Pi

http://www.formfactors.org/developer/specs/4_Wire_PWM_Spec.pdf the link takes you to the specification for 4-wire PWM controlled fans. apparently you must use a PWM signal 25kHz. if you do not apply any signal and just float the PWM control wire the fan runs at full speed. to control the speed you w...

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