Getting started with imp002 and the breakkout board

I bought two imp002 and the breakout boards. Soldering done, now I connected two LEDs (red, green) and the photo transistor. When I power it (right now with the 3.3V of an Arduino, just for convenience), both LEDS are flashing. It is my understanding that I then have to use the Android/iOS software to try connect it… Other than a strange remaining flickering on my screen after the blink up, nothing happened. E.g. the LEDs continue flashing.

I probably should have bought the v1, I know, but now I have the v2. Is there a getting started guide out there? One that explains in detail what to connect where, which LED, phototransistor and all the resistor values?

Here’s what I did:

IMP GND to Arduino GND
IMP 3.3V to Arduinoo 3.3V

LED GREEN and LED RED are attached and use a 56k resitor which seems to work fine - LEDs blink when powered up.
OPTO BIAS connected to Photo Transistor Collector.
OPTO IN connected to Emitter. Also, the emitter is connected to GND via 100k resistor (just as in the spec).

So again, the LED’s flash. AFter the blink up process, nothing changes… any idea?

When using the Smartmaker breakout, I had to tie VREF to 3.3V. Also it is possible that the available current from the Arduino isn’t sufficient to power the board fully. I’m not sure of that, but it is something to check.

Edit - Just looked. The Arduino Uno can supply 50mA at the 3.3V pin. The imp002 spec sheet says that typical current draw during normal usage with WiFi is 80mA and can go up to 250mA.

For best results, keep the light in the room low, and put your phone as close to the top center of the phototransistor as possible.

If you like using the imp002, the Amber reference board gerber files are available in the dev wiki. There are a number of board houses that will let you produce small batches. I recently used SeeedStudio, who will let you produce as few as 5 boards. There is a bill of materials in an excel file with everything you need to order the parts from Digikey. Electric Imp has done almost all the hard work… you just need to order and solder. It isn’t a beginner soldering task, but with a decent iron and skills, its a really fun thing to do. The worst part was waiting three weeks for the boards to arrive.

Thx a lot. So the arduino is definitely not powerful enough. What would you use to provide the 3.3V?

Spark fun and adafruit both have nice breadboard power supply kits for 3.3v.

Hi again! I tried again but no luck. I have a 3V power supply… Do you think that makes a big difference? Both leds still blink orange, e.g. I need to run blinkup but it just does not work.

Vref is now also connected to the 3v.

If anyone still has some idea, please let me know.

One issue could be with the photo transistor - I bought these here which seem fine to me:

SFH300 from Osram.

The exact photo transistor wiring is as follows:

Opto Bias to photo transistor (longer pin, Collector), Opto In to photo transistor (shorter pin, Emitter). The shorter pin is also connected via a 100k OHM resistor to GND.

If someone else could post the exact wiring and components of a working setup, that would be really great!

imp002 spec sheet has everything you need:

You can’t go wrong ordering from Digikey, if they will ship to your location.

Can you see your impee in the IDE? It should show up as a new device in the upper left. If you can, you are good to go, and your LEDs are just connected wrong.

You can try wrapping non-clear tape around the phototransistor so that only light from your phone is able to get into the P-T, this is similar to putting your fingers around the imp001.

I think you might have the photo-transistor in backwards. Unless I am reading the data sheet wrong, the collector is the shorter pin, and the flat side.

Hi Joel, many many thx for your replies. I was not working on the imp for some time and just saw one of your posts with regards to the imp002 and gave it another try. I am definitely a bit further now.

… I was about to tell you that nothing worked, but now I just saw the imp connected for the first time. It’s a bit weird. Here’s a few things that might help others.

  • The bias resistor for the SFH300 that I am using needs to be higher that 100k - I am using 480K now. I was using my new Nexus 5 initially and got it connected later on using a Nexus 4 in a darker room. I think a bias resistor in the >600K range is also not working, or maybe just something was wrong with the lightin or so…

Connected - so now I can finally try stuff out. Exciting, thx a lot!

Electric Imp now has more documentation available on the bias resistor values, but for use with the recommended phototransistor, they are recommending values under 100K… such as 47K and 68K.

One thing that all of us that are using the Smartmaker breakout need to remember is that it doesn’t have the capacitors that are recommended whenever you use the Imp module.

Glad you got it going!

Has anyone tried the RadioShack device:

Infrared Phototransistor
Model:276-145 | Catalog #: 276-145

Are you aware this is an infrared device? I would think it’s likely not going to work in the blink-up circuit if that’s what you’d be trying to use it for. (I’ve not played with the detection circuit at all … others are much more versed than me re: this. I just recognized the part you referenced is not a visible range phototransistor, so may not have the response you want/need).

Phototransistors are generally most sensitive in the IR wavelengths, but you want one which does not have an IR filter on it.

This radioshack part looks like it’d work fine, if indeed the picture is representative (clear lens, no internal filter visible). The ones that are problematic are the ones which look black - ie, they block all visible light and only pass IR through to the silicon.

Thanks for the elaboration Hugo. Yea, just a quick response from me suggesting something with a spectral response skewed towards the visible range might be more suitable. (Hard to tell without any specs on the RS device). But the unfiltered IR parts likely have sufficient visible sensitivity as you suggest.

Sorry, wasn’t meaning to be dismissive of your reply! The radioshack part is worth a try, but there’s often a huge difference in sensitivity between devices so you may find you need much more or much less resistance in the bias than the suggested parts.

Generally phototransistors seem to have mostly the same sensitivity profile, and it’s which bit of the spectrum to pass to the die which makes them visible/red/green/blue/IR/clear/etc. From reading the wikipedia page it seems like the profile is a result of which semiconducting material is in use:

No worries Hugo … I was a bit quick on the draw with an initial response without researching a bit further. (My previous experience with IR devices was to detect IR :slight_smile: … so I made some assumptions that they might not as suitable for the blinkup circuit). Thanks for the link and explanations about the filtering … always good to learn about things in more depth!

Thank You for your comments.

I did pickup some LTR-301 from Digikey.

With a 50K (2x100K in parallel) series resistor, it all works fine.