Engineering Project

[mpaterson]

Hello
I'm new to the raspberry Pi forum so please forgive me for any mistakes I make!

We're doing an engineering project with school and I have some questions on the compatibility of parts that we're using.

We're planning to use a raspberry Pi b+ with the Pi noir camera (http://www.raspberrypi.org/products/pi-noir-camera/ (similar to the picam I believe, and this DIY pan /tilt kit (http://blog.dawnrobotics.co.uk/2013/10/ ... pberry-pi/) to make a surveillance unit. We were also planning to add IR lighting such as this (http://www.pi-supply.com/product/bright ... pberry-pi/). My question is are all of these parts compatible (will there be enough space on the GPIO header) and will the Pi have anough to power all parts? If not how can i power them externally?

Another question is, if we used another B+ as a base/control unit outputting to a screen could we get the two pis to cnnect using a standard WAP and wifi dongle such as these?
http://www.amazon.co.uk/Edimax-EW-7811U ... B003MTTJOY
http://www.amazon.co.uk/Edimax-EW-7416A ... cess+point

Thanks in advance for anyone taking the time to answer this post

[Burngate]

Regarding space on the header - you should have no problem.
The camera, be it the ordinary one or the Noir (they're identical, apart from the infrared filter, missing on the noir) will not take up pins on the header.
The pan&tilt kit uses 2 GPIOs for PWM, ground and +5v. If you decide to power it separately then you will have to connect the negative of the external supply to the Pi's ground.
The IR light also uses 2 GPIOs - I2C clock & data - ground and +5v. Again, separately powering it will need the negative of the external supply connecting to the Pi's ground.
Since there are two +5v pins and seven ground pins on the header, you should have no problem there.

Power, though, may be an issue.
There are two considerations - what the supply feeding the Pi can provide, and how much of that is available after the Pi itself, the camera and any USB dongles have taken what they need, bearing in mind the polyfuse on the Pi.
Neither the Pi Supply* nor the Dawn Robotics sites seem to say how much current their devices use, so it will be a case of suck-it-and-see.
I would plan on using an external supply for both, just to be on the safe side. If you find you can use one supply for everything, you could consider supplying the Pi through its +5v pin on the header (through a fuse).

As far as comunication is concerned, WiFi should work as you suggest, though there are probably far too many threads here for you to find all the information available.

*Two more black marks against the Pi Supply Bright Pi device.
It appears to use LEDs with built-in resistors - I'd much rather have separate resistors
The picture seems to indicate that they use orange wire for ground and green for +5v. Wouldn't it have been better to use black or green for ground and red for power? Or am I just too pedantic?

[mpaterson]

Hi

First of all thank you very much for taking the time to answer my post.

Secondly would a cheaper IR led source such as this http://www.amazon.co.uk/Infrared-Illumi ... ds=IR+leds
be more preferable if at all?

Also how would you suggest externally powering lighting / movement , and would this still allow for control from the raspberry pi?

[Burngate]

To power externally, do something like:

pan_tilt_pi_circuit_with_battery.png (28.12 KiB) Viewed 1611 times

(grabbed from the Dawn Robotics site)
You can do a similar thing for the light.
So long as there's a common ground, so that the reference for the signal voltages is the same, and the device recognises the Pi's 3v3 output as a high, and the device doesn't put out more than 3v3, it should work

Both those devices appear to be happy with a 5v supply and the Pi's 3v3 GPIOs, whether supplied from the Pi or externally.
If you wish to use higher voltages, you'll have to check what's happening.

That Amazon IR source may well work. However there doesn't seem to be much information about current, voltage, etc. so you'll have to do some research. Welcome to the world of electronics!
If it were me doing this, I'd buy one just to see if it did what I want - it's what I did when I worked for Thames TV, and they went out of business. Must have been a coincidence.

[mpaterson]

Thanks very much once again,

http://www.ebay.co.uk/itm/5V-2A-2-5mm-U ... 1332208760
Would a Power supply such as this work if we could cut of the end and attatch the wires somehow?
Or would it provide too much current?

[davidcoton]

If the supply VOLTAGE is correct, too much CURRENT is not an issue. The thing is to have enough current available, too much doesn't matter.

If the VOLTAGE is wrong, it will not work. Too much voltage can cause permanent damage.

@Burngate While red (positive) and black (negative) has been a UK de facto standard for DC for many years, with the change of mains wiring to brown (line) and blue (neutral), colours are now specified in Wiring Regulations for DC wiring (brown positive, blue midpoint, grey negative -- but earthed "negative" is blue) as well. Note this is not applicable within a device, only for fixed installation wiring. Before anyone nit-picks, read the wiring regs, after that you will feel so beaten up you won't want to reply! (Edited twice to correct DC colours)

[rpdom]

@Burngate While red (positive) and black (negative) has been a UK de facto standard for DC for many years, with the change of mains wiring to brown (line) and blue (neutral), these colours are now specified in Wiring Regulations for new DC wiring (brown positive, blue negative) as well. Note this is not applicable within a device, only for fixed installation wiring. Before anyone nit-picks, read the wiring regs, after that you will feel so beaten up you won't want to reply!

As Mains wiring is AC, not DC, the changes in regulations have absolutely nothing to do with the colours used in the wiring shown.

Perhaps you should re-read the wiring regs?

[mpaterson]

Thanks again

So what you're saying is that it would work?

If so would it be feasible just to split the ends and use strip connectors to connect the power supply with the lighting / movement?

[davidcoton]

As Mains wiring is AC, not DC, the changes in regulations have absolutely nothing to do with the colours used in the wiring shown.

Perhaps you should re-read the wiring regs?

I just have. I made one slip, negative should be grey (blue is midpoint).
See "Requirements for Electrical Installations" 17th Edition Appendix 7 "Harmonised Cable Core Colours" Table 7E "Example ... d.c. installation ... ". Wiring regs apply to DC as much as AC. As I said, they do not apply to internal wiring of a device or appliance. That's why all sorts of odd colours can occur. But the standard (for installation wiring) is now brown and grey, not red and black. Note also it is not a "Regulation" within BS7671 (the wiring regs), the appendix is informative but refers to BS EN 60445 and BS EN 60446. Again these do not seem to cover the internal wiring of a device or appliance.

EDIT: Arrgh! DC Can be brown/blue, if (as in most common circuits) the negative is earthed. Read the Wiring Regs if you really need to know!

[plugwash]

Also note that BS7671 aka "the wiring regs" is not and has never been a legal requirement.

[davidcoton]

Also note that BS7671 aka "the wiring regs" is not and has never been a legal requirement.

True. However, following the wiring regs is a way of demonstrating that the design and construction of the installation is safe and conforms to Building Regs, Health and safety at Work, and other statutory regulation that may be relevant -- quite apart from keeping insurers happy. The degree of knowledge and experience required to demonstrate that a non-compliant installation is safe is considerable and should not be undertaken lightly.

Way off topic, and only relevant to a small number of RPi projects

[Burngate]

http://www.ebay.co.uk/itm/5V-2A-2-5mm-U ... 1332208760
Would a Power supply such as this work if we could cut of the end and attach the wires somehow?

I could be wrong, but that seems to be just a cable!

So what you're saying is that it would work?
If so would it be feasible just to split the ends and use strip connectors to connect the power supply with the lighting / movement?

5v 2A supply --- some sort of connecting system --- two separate pairs of wire, one to the Pi, the other to the lights & pan/tilt.
Yes that would work


And ignore most of the intervening posts - we pedants get carried away sometimes