What sensors can I use?

[pmp4]

Hi.

Can I start by saying how much I love the Crumble.

I bought the Cam Jam kit from PiHut. I wanted to use the temperature probe and possibly measure light and sound levels. Theses would inputs would be triggers. The problem is they only seem to create levels of Hi or Lo.

For example, I wanted to program the Crumble to trigger an output when sound wwas over a certain Decibel level or trigger an output when light or temperature reached a certain level.

Is this possible?

Thanks

[Simon]

What sensors are they?

[n000dle]

Hi,

I’d also be interested in using a temperature probe with the crumble.
On looking into the CamJam sensors kit it says that the temperature sensor is a dallas DS18B20 encased in a waterproof housing, if that helps?

I’ll be looking forward to seeing whether this can be achieved as I am building a light setup for my tropical aquarium, and might just expand it to include a thermometer/temperature alert system if it’s possible!

[Simon]

The DS18B20 needs special code to read its output as it send the temperature in a digital format (known as 1-wire)
Something like https://www.sparkfun.com/products/10988 should work as it produces a analog voltage output but I’ve not tried one myself

[Simon]

I’ve just ordered a couple to see if they’ll work with the Crumble 🙂

[n000dle]

Would this also work with a k-type probe?

[Simon]

My TMP36 came and I can confirm it can be used with Crumble 🙂

@nooodle What’s a “k-type” probe?

[n000dle]

something like this? I don’t actually know what’s in it… :/
On closer digging I don’t think it will be suitable anyway, as unless I cover the metal with something it could leach into my tank…

[Joseph]

Hi all,

Sorry about the slow reply. Currently the Crumble can only sense analogue voltages. As Simon said, the DS18B20 uses a digital signal to communicate. It is on my todo list to support, though. I’ve also got some more sophisticated sensors on “Crumbs” coming soon, here’s the temperature one:

Currently, to meassure the temperature of water, I’d probably use a stainless steel-encased thermocouple (like the one n00dle linked to), with an AD8495 chip (Adafruit do a nice breakout board) to get an analogue voltage.

All the best,

Joseph

[pmp4]

HiJoseph.

What’s the latest on the sensors?

Thanks

[EricColen]

@Jospeh, i also want to know something. What level of analog voltage level it can measure? Also what amount of current it can tolerate?
Also how you made your thermocouple using the stainless steel scale?

[Joseph]

@pmp4 Sorry, I’ve not made much progress on the DS18B12 comms yet. Realistically, I’m focussing on getting the linux version out in the next week or two, then I plan to come back to the Crumbs (and possibly the DS18B12).

@EricColen The Crumble will convert a voltage between 0V and the power supply voltage (e.g. 4.5V) to a number from 0 to 255 (i.e. 8-bit).

We don’t have immediate plans for a “Crumble” thermocouple, but it should be possible to use 3rd party add-ons. The temperature Crumb pictured above won’t be submersible.

Joseph

[MintTech]

Hi,

I’ve got loads of old Lego RCX equipment in school and I was hoping I could use the touch button sensor as well as the light sensor with the Crumble. I managed to get the touch sensor working breifly but it was a bit hit and miss and now it’s refusing to work with the Crumble. The light sensor hasn’t worked at all. Has anyone used these sensors with the Crumble and got them working?

I read a post somewhere that for the light sensor you had to set the output high to charge the sensors capacitor then take a reading 1ms after. I’ve not had any success. Is it just because the Crumble is 4.5v and the Lego RCX sensors are 9v?

Any help appreciated. I can include pictures of the sensors if that helps.

[MintTech]

I’ve got the lego rcx touch button sensor working now – just connect as if it were a normal switch in the crumble getting started guide and read input as high or low.

After further research the Lego RCX IR light sensor needs to be “charged” – a capacitor stores energy and then the value needs to be read from the input shortly after. Can anyone sugges a way of doing this in the crumble software? Can I set an output as High and then back to an input to read a value into a variable?

Here is some sample code I found online and a description of the timing – https://seriousrobotics.wordpress.com/2011/11/20/using-rcx-lego-sensors-with-arduino/

[pmp4]

Hi Tom

any news on the DS18B12 comms yet?

I am eagerly awaiting the sensors.

[Author]

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