Let me help you #MakeYourOwnBits

HI @Car0line,

Again good questions!

Always connect all the VCCs and GNDs together. This makes your Bit modular with the rest of the littleBits. (the ProtoBit gives you the option to disconnect them but I dont see a reason for that)

What you do with the SIG IN and the SIG OUT is up to you. There are in general 2 configurations.

  1. SIG IN == SIG OUT. Put the jumper in between on the ProtoBit. In general only used for OUTPUT Bits. Use this if you only want to read (use) the SIG IN but not want to change the signal. You just connect the SIG IN to SIG OUT. (Note that it now makes no difference where you connect your circuit, on the top or on the bottom of the ProtoBit) E.g. see my RGB LEDstrip Bit: http://littlebits.cc/bitlab/bits/individually-controllable-rgbstrip-bit

  2. SIG IN != (is NOT) SIG OUT. Remove the jumper in between on the ProtoBit. In general only used for INPUT Bits, LOGIC Bits. Use this if you want to read the SIG IN and based on that make some kind of SIG OUT.
    E.g. my Radio Bit: http://pv-productions.com/radio-bit/. But also the MP3 Bit, the CloudBit, LatchBit, InverterBit etc.
    Also it is possible to only do something with the SIG OUT and don’t use the SIG IN. E.g. for your pressure sensor and my NFC Bit: http://littlebits.cc/bitlab/bits/near-field-communication-nfc-bit

Hope that clears some things out:)

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@Philip_Verbeek thank you for posting and offering your help! Your creations are inspiring!

I’m trying to build my own modules and have been struggling one with the DAC portion as I’m not an electrical engineer. From what I can tell from https://github.com/littlebits/w6-arduino/blob/master/hardware/LB_BIT_w6_ARDUINO-v03(4-5)/LB_BIT_w6_ARDUINO-v03(4-5)OHW.pdf?raw=true, the DAC used in the arduino bit is a 3bit R-2R resistor ladder.

From reading about R-2R ladders it seems the little its design varies in that it’s using capacitors, resistors, and amp, and a diode. Makes me wonder if it’s actually a low pass filter.

Is there any more details anywhere on how the littlebits team does their DACs? This would greatly help me build my own.

I used an mcp4725 breakout in my design, but would like to simplify the design and not use the i2c pins if possible. https://github.com/shaiss/LittleBitsUltrasonicRangeSensor

I found a TI 0800 DAC, but I think it’s overkill as it seems like anything above 3 or 4 bits is overkill.

Thank you,

Hi @shaiss,

Thanks, Actually I also build a DAC in my NFC module.

You are right at some points.

All it takes to make an Analog signal from PWM is a one stage low pass filter using 3k9 Ohm resistor and 10uF capacitor. You can vary the value to see what works best for you. See picture below.

At littleBits they use a 3 stage low pass filter to do some extra filtering for even higher frequencies.

The opamp is configured as a buffer. This may be necessary depending on the load on the output pin. Note that they use a Rail to Rail opamp where the output voltage swings are very close to the VCC and GND.
E.g. if you use a UA741 or a LM324 you see that the max output is e.g. 0.5 volt below the VCC and 0.5 volt above the GND etc.
(You can google at sallen key filter for the background)

The diode you can leave out for prototyping. This only protects the Bit against static voltages.

If you still want to go with breakoutboard I would suggest a 8 bit DAC. This gives you a resolution of 5volt / 1024(8bit) = 5mV. This is the same as the Arduino and works fine.

Hope that helped. Let me know if you have any other questions.

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So I can leave the opamp out for simplicity and prototyping?

I’d rather not as I’m using the mcp4725 and it takes up more room than I want on the photoboard and additional code on the arduino I can leave off. And additional pins.

Thanks for the detailed reply. What’s a 3k9? Is it a resistor? And 10uf a capacitor?

Sounds like a low pass filter would be best in this case. Do you have any pictures or simple diagram of what you used in your nfc bit? Thank you!


Yes indeed. But it depends of your load on the output. The buffer makes sure the circuit before the opamp is seperated from the output. But for prototyping I also leave it out most of the times.

A 3k9 Ohm resistor and a 10 uF capacitor indeed. I read over it. I changed it above.

A low pass filter would do good indeed for your use. Below you can see one of my very very simple low pass filters. But also try different values to see what works best for you. or add another step etc.

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btw @shaiss,

Now you have your circuit somewhat all prototyped and working, did you think of shrikify your project on e.g. a ATtiny85/84?
Take a quick look at this: Programming ATtiny chips


I actually started it on an uno. Then moved to the nano. Now I’m moving it to a dfrobot cheapduino. Maybe after that will be a standalone atiny.

Just to confirm. When you say 3k9, that’s the same as 3.9k?

Thanks for the diagram. I’ll test it out soon as I can.

Correct, 3k9 ohm aka 3.9k ohm aka 3900 ohm

Had a few minutes to test and I think I have it figured out. While not exact as I didn’t have the time to do the math I used a 10k ohm resistor and a 104 0.1uf capacitor and it works on the breadboard. I’ll have to update my module to use this soon.

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Successfully moved to the dfrobot cheapduino and ditched the mcp4725 for an LPF. I used the same values as before and there’s a slight dim Inbetween but it looks nice.

Thank you so much for the help!


Looks great Shai! The device is very responsive from the look of your video. Thanks for designing it in the open here. I think we all learned something here.


Thanks @chris101 ! The full codes at https://github.com/shaiss/LittleBitsUltrasonicRangeSensor. I still need to update the diagram to reflect the LPF.

It’s people like @Philip_Verbeek & @JackANDJude who we can thank for really showing us non-engineers what’s possible!

Congrats @shaiss!

Great job, learning and sharing!

I agree with @drthuler and @chris101 … Thanks for sharing and documenting your work in progress, @shaiss! Do you have project ideas for your range finder module?

HI everybody,

I’m getting all my ducks in a row in preparation for submitting our SoundControl module to the bitlab. I have a few questions however. Once I submit the module, how long before the module shows up for voting and what type of changes can I make to my submission (text, video and such) during this time. Can I tweak things after voting has begun?

Should I expect to receive any feedback (changes or suggestions) from LittleBits before or during the voting process or only once (hopefully) the module has recevied 1000 votes. Lastly, Once a module has passed the voting hurdle, do you know what engineering tasks will the LittleBits folks be responsible for vs. me and my engineering partner?

I know you all have been down this road many times before. Anything else you think I should know or you wish you had known (or asked) before you submitted?

Thanks so much for your help,


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I built the module in response to my 6yr olds challenge that he wanted a range sensor to use with his littlebits so he can make some circuits he has ideas for.

So far he has the idea for an intruder alert if someone try’s to sneak a cookie and to alert if the door opens a certain amount.
Here’s the video we made for the bitlab submission https://youtu.be/a5Vv4K6MEeY


Hi @joey,

From my experience I can tell that it can take up to a month from submitting the Bit till finally being published. This may vary because littleBits plans the publishing of Bits tactical etc.

For my RGB LED Bit, Andrew, of littleBits back then, asked me to use other music due to copyright claims etc. He kept me updated on the progress. Also if I wanted to change description text or images I could contact him for that.

For my NFC Bit, Dennis, of Bitlab back then, just kept me up to date on when they would publish it. Also I asked him to edit the description text and images for me.

For the Radio Bit, Syed directly contacted me that they would discuss it over the next week and after a month he mailed me again that the Bit is published.

For all my Bits I never got feedback and are just the way I designed them. LittleBits also wants the community to respond on the Bits etc. look at it from a different kind of view etc.
I think littleBits will only give feedback if there’s some kind of good reason. Not specific to the design etc.

Hope that helped.

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I submitted mine two weeks ago and it’s still in a “pending review” status. It’s also locked to any changes. So I doubt you can make changes after its open for votes.

Im gonna find out the answers to your other question soon as mine opens for votes. Good luck!

You can’t change the text, video and images yourself after submitting. But you can mail your contact person from littleBits to change it for you. That’s what I did at least.

Wow. Thats longer than I thought but I guess they probably have a backlog of modules they are working thru. I would love to know how many modules get submitted a month. It would also be great if LittleBits published a list of those modules that did not get enough votes. I think we could all learn a lot from studying that list.

Thanks so much for your help @Philip_Verbeek

you too @shaiss