Interesting…I lived in Tamil Nadu for several years, working with a ngo there…however I have to ask…how many mAh does the board use as my raspberry pi is gonna run on batteries

It does look very interesting! Out of interest, does it have a RTC? Just a thought because it currently appears to log via a PC and I guess that switching over to using a Pi instead means that you lose the ability to record experiment timestamps.

Time for your habitual “don’t forget to resize massive photos before putting them on a website” reminder, I think :)

looks nice

As long as the price is low and the software interface is good, nothing can go wrong really :D

I also don’t remember hearing anything about the measurements mentioned in this news article, while I did take advanced physics at high school.. Perhaps they were too expensive back then

Looks great. Is it at the stage where interested parties can get hold of one or still too early?

This is genius! Keep up the hard work. You will be a big part of helping these kids learn at a low cost. Just genius.

Love it! This is what we’ve been waiting for

Hi,

The boards and the concepts mentioned look very interesting. Will it be possible to self assemble these boards?

Concerning a time stamp within the DAQ setup, would it be possible to build a board with a clock chip and a FIFO? In this manner one might be able to make many samples quickly and then read them out.

Often slow control for experimental setups is required to control high voltage or high current outputs. For example, electric heaters (high current) and bias for detectors (high voltage). Some similar functionality may prove useful. A typical array of sensors might be thermocouples, humidity sensors, photo diodes, pH probe, silicon panels, GEM detectors etc..

Best regards,

Will

When we can get is from a store? It is already months passed.
Let go with beagleboard. I cannot wait any more.

All we need now is a well priced HDMI Monitor that we can use with our RaspberryPi’s…
I have yet to find one new for under $50!

Lots of exciting possibilities for signal processing and control using the Raspberry Pi and expEYES.

May I make a plea for future versions to include some galvanic isolation somewhere in the communication connection “string”. Apart from the safety issues the “system” ultimately connects through the TV/Monitor ground connection, that is if it has one (My 32″ LED/LCD Samsung TVs do not). Without a grounded TV you will have the permitted leakage (at some high frequency) from the switch mode power supply in the TV. This could/will play havoc with some A/D measurements.
In the lab it is very easy to put a battery operated DMM across a voltage source to measure it. The DMM is isolated so no problem. TV (or monitor)+RASPi+expEYES is not isolated.

I have several 6.5 digit DMM that are driven from the mains supply and they go to a fantastic length to:
(a) provide safety isolation from the mains (CAT II 300/600/1200 volts)
(b) negligible leakage.

OK so these are high end devices (£700 a time) but none the less the same principles apply.

TVs and monitors are not intended to be hooked up to real world experiments so there may be risks with some “el cheapo” brands.

Not to be to alarmist about it but we have a friend whose young daughter was killed by an inadequately earthed shop till.

So make it safe for the kids to use and make the measurements mean something.

I love the idea of RaspberryPi + expEYES

Will RS sell it as well?

I would love to get an ExpEYES here in the US. Any possibility of finding a distributor here?

Not just kids, Bjorn!

I’m looking for something similar for a humidity control system for my damp-ish basement.

I’ll need to calculate whether air pumped from the exterior at a given temp and humidity will actually absorb humidity from the basement walls for expulsion, or actually – when its temperature is dropped to that of the basement – actually condense water out and worsen the problem.

Numerous humidity and temperature sensors will be required, plus control of fans, etc. Early days, but this is a really encouraging find.

David’s point about earthing and safety is essential. Earthing, grounding, 0V refs are nothing like as simple as they sound, and safety must be the first priority

There should be very clear documentation about this with the product, preferably with clearly explained and illustrated dos and don’ts.

Best wishes,
Steve

Ajith

The shock you got from the laptop was probably the leakage from the laptop power supply. The output of most notebooks/laptop power supplies consists of two wires and usually neither of these are earthed. They rely on “double insulation” for their CE/UL safety approval. As they are switching power supplies they generate a high frequency leakage current across the internal safety barrier (ie the switching transformer). These currents have to be within a permitted range. This leakage current will flow through your body to ground and can cause some “tingling”. From memory the permitted current is ~2mA (I could be wildly wrong so do not rely on that figure)
How do I know this – well the same happened to me and I was responsible for shipping many thousands of note books, mild panic resulted until I had checked it out!!!!
Many monitors/TVs have similar issues.

So there is a safety issue if the leakage current is too high.

However there is another issue and that is where this current finds a way to ground/earth through the experiment. You are using a 12 bit A/D so even micro-amps of leakage can mess up the readings.

What I would humbly suggest is that you were to put two opto isolators in the Tx and Rx lines to the AVR microcomputer. Power the USB side of the unit from the USB host and power the rest from a separate power supply such as a wall wart with a traditional 50/60Hz transformer (you power demand is minimal) or at least one that you can insure is connected to ground/earth. That way you would remove yourself from earth leakage issues from laptop/monitor/TV power supplies.

This will probably slow the whole thing down (I do not know what baud rate you are using for the AVR) unless you use quite expensive opto isolators (10 Mbits/sec 6n317 100+ price ~0.40 GBP). They need to be quite fast as the AVR UART can not tolerate much distortion (<3%) [ 10 Mbits/ sec sounds fast but in this case you could be limited to ~<50 Kbaud once you take account of worst case rise, fall and propagation delays]

Hope that helps

BRGDS

David H

Not only a replacement for the BBC micro – but a VELA (http://www.retro-kit.co.uk/VELA/) for a new generation

I want this to go with my Raspberry Pi when it arrives although learning how to use it will take ages for me!

Sir, i want to interface temperature sensor to the expEYES ,i cant interface it directly so pls tell me how to interface.tell me the ckt diagram.

expEYES Junior USB version has been tested with Raspberry Pi. It now works perfectly fine.
http://expeyes.in/sites/default/files/Experiments/rpi-eyes.png

Dear Sir,
Here at physics department we are interested to introduce for M.Sc students. We have your expeye kit and Rpi board and 12″ LCD. I have downloaded OS and display is OK.
I need to know port pins to be used for interfacing Rpi with expeye kit.