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by Tage
Fri Nov 21, 2014 3:15 am
Forum: General discussion
Topic: SSR Relay directly to GPIO
Replies: 7
Views: 12978

Re: SSR Relay directly to GPIO

1. beware of anyone suggesting that you use a Darlington array to power anything by the Pi. double check their information.
2. the data sheet for the solid state relay does not give a good impression. they cannot clearly state how to drive the input - stay away from such products.
by Tage
Tue Nov 18, 2014 1:50 am
Forum: General discussion
Topic: Powering Raspberry Pi B+ Permanently From Solar Panel
Replies: 10
Views: 3734

Re: Powering Raspberry Pi B+ Permanently From Solar Panel

you need to calculate how many watt hours you need per day. http://www.raspberrypi.org/forums/viewtopic.php?f=29&t=91172&p=640568#p640568 I did a quick estimate on how large solar panel I need to power a 4W load year round, and the result was that I need a 30W panel and a large battery. I live in Ca...
by Tage
Fri Nov 14, 2014 3:35 pm
Forum: Advanced users
Topic: Time with 6v lantern battery
Replies: 13
Views: 3333

Re: Time with 6v lantern battery

Here is the link to the sunshine data.
http://solarelectricityhandbook.com/sol ... iance.html
If the data and the calculations are correct you would need about 3.6 times larger panel in the UK than in California. Probably more because you may have a larger number cloudy days in a row.
by Tage
Tue Nov 11, 2014 11:00 pm
Forum: Advanced users
Topic: Time with 6v lantern battery
Replies: 13
Views: 3333

Re: Time with 6v lantern battery

In case somebody is interested, I did a quick estimate on how large solar panel and battery I would need to run my Pi nonstop, and came to the conclusion that the minimum panel size is 30W and the battery size is around 35Ah 12V. That is if I adjust the tilt of the panel so that it is optimal for th...
by Tage
Fri Nov 07, 2014 4:09 am
Forum: Automation, sensing and robotics
Topic: How do I? Turn on 12v IR LED from PI?
Replies: 12
Views: 6725

Re: How do I? Turn on 12v IR LED from PI?

it is true, BS170 is not suitable for driving much current at 3.3V gate voltage. the data sheet shows that. you can perhaps use it to drive another transistor that then provides the load current. but why add all those components when one single MOSFET with Rdson specified at 3.3V or below is availab...
by Tage
Thu Oct 30, 2014 10:35 pm
Forum: General discussion
Topic: pi solid state relay pulse width modulation?
Replies: 31
Views: 5809

Re: pi solid state relay pulse width modulation?

you are talking about a single cell Li Ion rechargeable, size 26650, with nominal voltage 3.7V and 3.5Ah capacity. so you need three of those connected in series for 11.1V. this string will give you 39Watt-hour, so you will have to add several of these strings to get the high power you need. not eas...
by Tage
Thu Oct 30, 2014 9:41 pm
Forum: General discussion
Topic: pi solid state relay pulse width modulation?
Replies: 31
Views: 5809

Re: pi solid state relay pulse width modulation?

some question marks remain, but here is a schematic for a power driver. two 40V 0.0015ohm MOSFETs type TO-220 mounted on a heatsink. one gate driver with its input connected to a GPIO output that delivers a PWM signal that makes it possible to regulate the heating power in the nichrome element.
by Tage
Thu Oct 30, 2014 8:54 pm
Forum: General discussion
Topic: pi solid state relay pulse width modulation?
Replies: 31
Views: 5809

Re: pi solid state relay pulse width modulation?

it appears like a relatively simple problem except for the power level. you would need a large 12V battery and a MOSFET that you pulse width modulate from a GPIO output. if you drive the MOSFET directly from the GPIO it will switch too slowly so it will heat up. so you need some type of gate driver ...
by Tage
Wed Oct 29, 2014 3:08 pm
Forum: General discussion
Topic: pi solid state relay pulse width modulation?
Replies: 31
Views: 5809

Re: pi solid state relay pulse width modulation?

it is relatively simple to create an adjustable constant current source using a switch mode regulator. for example, take a buck regulator (step down regulator) and connect it to a dc voltage, then use PWM on a GPIO output and an RC filter to create an adjustable control signal that is applied to the...
by Tage
Tue Oct 14, 2014 2:13 am
Forum: Beginners
Topic: Check Out This Setup! Thoughts! Carputer!
Replies: 9
Views: 1545

Re: Check Out This Setup! Thoughts! Carputer!

I don't think the solar charger shown has any value. the solar panel is too small, and why adding a Li-Ion battery if you have the car battery? just get a solar panel with a charge controller and connect it to the car battery, then you can afford to connect a Pi to the car battery - provided that th...
by Tage
Wed Oct 08, 2014 12:55 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Turning on MOSFET with GPIO crashes Pi B+
Replies: 11
Views: 2356

Re: Turning on MOSFET with GPIO crashes Pi B+

I suggest that you add a 1k resistor between the gate of the MOSFET and the GPIO pin. the reason is that your layout is very much spread out with long wires. so you don't want to switch the MOSFET very fast. It will create problems. you may have some MegaHertz oscillation in your MOSFET circuit beca...
by Tage
Fri Jul 18, 2014 2:06 am
Forum: Camera board
Topic: a China knockoff version of R-Pi camera board
Replies: 54
Views: 21143

Re: a China knockoff version of R-Pi camera board

you have some good points here. one reason why I am quite critical regarding things made in China is because I have been there. at one point in time, I was for no fault of my own responsible for product development in Shanghai. The main owner of the company had decided that he could make money by mo...
by Tage
Tue Jul 15, 2014 1:31 am
Forum: General discussion
Topic: Pi Lipo charger
Replies: 5
Views: 3047

Re: Pi Lipo charger

I recommend that you add circuitry that level shift the individual cell voltages to GND where the ADC is. you should also add hardware circuitry that will cut off charging the voltage of any cell exceeds the safe rating.
by Tage
Fri Jul 11, 2014 1:51 am
Forum: Camera board
Topic: a China knockoff version of R-Pi camera board
Replies: 54
Views: 21143

Re: a China knockoff version of R-Pi camera board

My question is: how do you all respond to a situation like this where Chinese scam artists copy a design and markets it at a lower price without bothering about even trying to pass EMC regulations, electrical safety tests and such crap (more of an issue with relay boards). Do you just shout "Bingo!"...
by Tage
Tue Jul 08, 2014 2:47 pm
Forum: Automation, sensing and robotics
Topic: Solar Powered Raspberry PI + Modem, What do i need?
Replies: 1
Views: 995

Re: Solar Powered Raspberry PI + Modem, What do i need?

When dealing with solar power you need to start thinking in Watt hours. The panel size and battery size will depend very much on where you live. Take this example: you live in a location where the average number of Watt hours per m2 per day (reaching a solar panel that is tilted at the correct fixed...
by Tage
Fri Jul 04, 2014 9:26 pm
Forum: Beginners
Topic: Can a 3.7v lithium ion battery power a Pi?
Replies: 9
Views: 18895

Re: Can a 3.7v lithium ion battery power a Pi?

If you want to run the Pi off 5V you will need a boost regulator. one example is http://www.linear.com/product/LTC3422 the battery will deliver a relatively stable voltage until it is near empty, but unless the battery has built in electronics you must add circuitry to disconnect the Pi from the bat...
by Tage
Fri Jul 04, 2014 3:37 pm
Forum: Other projects
Topic: 100% solar powered RPi
Replies: 7
Views: 1903

Re: 100% solar powered RPi

I watched the video myself, thanks for the link. It must be the most annoying video I have ever seen. 32 minutes of ranting, with only a few facts. However, he brought up some good points. There are definitely obstacles on the road to solar powered roadways that should not be ignored. I had a quick ...
by Tage
Wed Jul 02, 2014 2:23 pm
Forum: Other projects
Topic: 100% solar powered RPi
Replies: 7
Views: 1903

Re: 100% solar powered RPi

If you intend to run the Pi on solar power alone, continuously, you are probably going to need at least a 60W panel and a quite large battery. It really depends a lot on where you live. I would not try any smaller battery than a 35Ah 12V lead acid battery even if I only intended the system to run du...
by Tage
Wed Jun 11, 2014 2:04 pm
Forum: Automation, sensing and robotics
Topic: Solar panel power output measurement with rpi
Replies: 19
Views: 5109

Re: Solar panel power output measurement with rpi

The solution will very much depend on how your solar panel system is configured. the simplest way to measure produced power would be to measure the voltage and current from the panels (dc). the measurement could be made by a separate micro controller and the data transmitted using wireless to your P...
by Tage
Sat May 31, 2014 1:48 am
Forum: General discussion
Topic: Can anyone suggest me a reliable relay board?
Replies: 31
Views: 6081

Re: Can anyone suggest me a reliable relay board?

I want a relay board so that I can control my lamp and fans, both connected to 240V AC. I thought of picking up one from ebay, however I am skeptical. (and also check the conversation here happened on raspberry pi subreddit) So can anyone recommend me a good quality relay board? Thank you! Make sur...
by Tage
Tue May 06, 2014 11:54 pm
Forum: Automation, sensing and robotics
Topic: Can i use this transistor instead of a relay
Replies: 78
Views: 12228

Re: Can i use this transistor instead of a relay

the saga continues. there are many ways to control a 5V fan from a 3.3V signal, I am sure. I am no expert (except when it comes to power electronics), but I think that most cooling fans have a little circuit board inside with circuitry that controls the motor. so one problem that may not be apparent...
by Tage
Tue May 06, 2014 1:39 am
Forum: Automation, sensing and robotics
Topic: Can i use this transistor instead of a relay
Replies: 78
Views: 12228

Re: Can i use this transistor instead of a relay

this is fun reading. this thread is growing and will probably soon contain the best collection of bad advice on the internet. ever. my suggestion is this: get an n-channel MOSFET that has Rdson (that is the ON-resistance) specified at 2.5V. so it will for sure turn ON whan 3.3V is applied to the gat...
by Tage
Wed Apr 30, 2014 2:35 pm
Forum: General discussion
Topic: Adjustable DC step down power n my design
Replies: 3
Views: 717

Re: Adjustable DC step down power n my design

This seems like a good solution.
by Tage
Wed Apr 30, 2014 2:21 pm
Forum: Automation, sensing and robotics
Topic: Sense direction of power flow
Replies: 31
Views: 7114

Re: Sense direction of power flow

with ac power, it is not as simple as just measuring the current. the current has an average value of zero and changes direction 100 times per second. to know which way the power is flowing you need to also measure the voltage, and compare the polarity of the voltage and the current waveforms. if cu...
by Tage
Sat Apr 12, 2014 1:00 am
Forum: Automation, sensing and robotics
Topic: Monitoring Battery Life
Replies: 5
Views: 2756

Re: Monitoring Battery Life

I have an additional question. In connecting an I2C or SPI, how do you read/extract the voltage value? I'm trying to monitor the battery life via a percentage and am wondering if it's possible to get the value and convert it to a percentage to output on a display. if you are using an analog to digi...

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