Let's Make Robots!

Robot Communications —How to talk to your robot. (Page 1)

This is the first page of an informative set of pages showing different ways to communicate with your robot.

The picture above is a 2 Watt Blue Laser I built several months ago. It's way too powerful for robot communications around the house (it would start fires), but it looked like a good enough illustration for this page.  :-)


All right, this is intended to be a somewhat comprehensive write-up concerning different ways to talk to your robot. Whether it will be all that comprehensive remains to be seen, but let's get started.

Okay, first up, let's investigate infrared. We humans cannot see infrared, but that doesn't prevent our robot from doing so. Some of the microcontroller chips already come equipped with the ability to decode infrared signals from something like a TV remote. (I'm thinking of picaxe here.)

However, what I want to show is simple schematics for circuits you can easily add to your robot. Let's call it modular design. First, here is a very simple sketch that shows how to drive an infrared LED. The input marked with the letter S must be driven with a different circuit such as a microcontroller. The benefit of using this circuit, is that it pulls much less current from the microcontroller output pin (Specifically, only half a milliamp).


But what if we want to make one or more of these infrared beacons, without using additional microcontrollers? Isn't there a cheaper way? Yes. I have drawn a couple different possibilities, which you could use on your robot. Here is a circuit using a 555 timer chip.


"How can I use that to send data to my robot?" That is an easy fix. One way would be taking the 555 reset lead off of V+ and switching it on and off with something capable of sending data, such as a microcontroller. (All you need is a small one like an 8 pin chip). The data or code coming out of a microcontroller would be input at the lead tied to pin 4 of the 555, with the 1 KΩ resistor there to limit the current. [Another alternative for inputting a modulation signal would be to leave pin four tied to the positive supply voltage and using pin five instead.]  This was not done because removing the capacitor from pin 5 might affect the stability of the oscillator.

 The 555 chip is nice inasmuch as it will drive several LEDs. What if you don't have a 555? Do you have a logic gate like a 7400, 7402, 7404 or others? There are a lot of different types such as 74LSxx, or 74HCxx and others. Don't let that confuse you. Any of them will work in the following circuit.


And to wrap up this page showing IR or Visible light signalling. here is one more pulser circuit and a detector circuit using the 38 kHz detectors which are available many places for low cost.

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Not only is the work precise and concise, but I like the approach.  Esepcially the gated one.  I'm using ATTinies for this right now which are comparable in price to both of these (at Digikey a 45 falls right in the middle between the NE555 and the 7404.)  If you have an Arduino and a breadboard you can program them just like an Arduino and it gives you μC level control/precision with fewer parts and less soldering (in my head it's 6 joints if you use a pre-regulated power supply.)  But it's definitely not as cool or as hands on as any of these approaches.  

I think it's important to learn what's inside the chips we're using, and the last schematic definitely gives you a sense of the magic that happens at the quantum level through these little black plastic components.

I don't buy from Digikey, but the prices I am looking at are a bit different.

I see NE555P's for $2.70, but that is a pack of 30 of them (9¢ each). The NE555Ns are $3.60 for 30. (12¢ each)

and for 7404s, the best deal I see here is a pack of 5 - 74HC04s (which also have the highest output of the 7404 family) for $2.29 (about 46¢ each) 

but the AtTiny chips (in the 8 pin DIP version) are selling for $1.50 each or $1.20 each if you buy a pack of 5 ($5.99)

so I still would put the AtTiny's as the highest.  –Besides I have bunches of 555s and 74xx04s in my parts cabinets for "free" (removed from old scrap boards), so for me and any other scrappers or hoarders out there, it is an easy question.


Finally the first page is published!! I'm saved!! Nice one dan!! If this page gets completed, it'll be the best source of info on communication available here!!

Although I hope that dan gets his problem sorted out asap as (just like he says in the description), I'm waiting for the robot communication article...

And dan, if you are shipping out viagra, can I get a few free samples? :P

max that was amazing as for you dan i recomand avg antivirus 2012 to remove your problem i run it on all my machines

Max you are the bomb................ and Dan good luck sorting it all out

Hey!  Sorry to hear about your technical troubles.

Since you haven't been answering your emails, I thought this was the best way to handle those requests of yours.  To answer your question, of course I'd like to help you reclaim your family's throne in Nigeria.  I must say I was a little surprised-you don't look like an Urhobo in your profile picture, but then what do I know?  It's not unheard of for Scots to marry into families throughout the Empire, after all.  I've gone ahead and wired the money to the account you mentioned.  It's very generous of you to offer to share that fortune with me, but it's really not necessary-one or two million will do.

As to that other thing, I don't remember when I told you about that particular problem but your solution is a Godsend!  At that price, I'll take as much Viagra as you can legally send me at one time.  Can we put it on my PayPal?

Finally, I'm pretty happy at my current job, but if things change, working as a mystery shopper sounds like a pretty sweet gig.  (I've always considered myself pretty mysterious!)  I can't take you up on it right now, but keep me on the bottom of your list and don't be afraid to bring it up again later.

Hope to hear from you soon,


(Tongue firmly in cheek.)