{"id":545,"date":"2019-08-25T16:04:10","date_gmt":"2019-08-25T16:04:10","guid":{"rendered":"https:\/\/www.protowrxs.com\/?page_id=545"},"modified":"2019-09-20T10:45:56","modified_gmt":"2019-09-20T15:45:56","slug":"lilliputian","status":"publish","type":"page","link":"https:\/\/www.protowrxs.com\/index.php\/robotics\/lilliputian\/","title":{"rendered":"Lilliputian"},"content":{"rendered":"\n
\"\"<\/figure><\/div>\n\n\n\n

\nn.
\nA very small person or being.
\nadj.
\n1. Very small; diminutive.
\n2. Trivial; petty.
\n<\/em>\n<\/p>\n\n\n\n

January 2014<\/p>\n\n\n\n

Back to Robotics<\/a><\/p>\n\n\n\n

\nLilliputian<\/strong> – seems like a pretty good description of this little\n fellow. Trivial, petty, diminutive, very small, etc. With all due \nrespect to Swift\u2019s Gulliver\u2019s Travels of course. Inspired by Yahmez \nMicRObot challenge, this is my 2.0 attempt. The first attempt is still \nthere and maybe viable for a future finish but I like this 2.0 layout \nmuch better. I just packed in as much as I could WITHOUT resorting to \nsurface mount devices (SMD) which I have no skills with.\n\n<\/p>\n\n\n\n

Size Matters<\/h2>\n\n\n\n
\"\"<\/figure>\n\n\n\n

\n\nAt least in the challenge so first I guess I should outline the current \nsize of Lilliputian. Currently the bot is about 35mm wide by 50mm long \n(not including the bumper horns) and 35mm tall. Total weight is 34 grams\n (1.2 oz). Not tiny by any means or as compared to some other entries I \nguess but small for me. I gave up some size for features which was the \nplan from the beginning.\n<\/p>\n\n\n\n

Chassis and Motors<\/h2>\n\n\n\n

\n \nLilliputian features a 3D printed base chassis of my own simple design \nto mount the two GM15 micro motors. To keep things narrow I offset the \nmotors and wheels giving it a bit of a goofy stance but making it much \nnarrower than traditional back to back mounting. That is where some 90 \ndegree gear motors such as those recently sourced by Yahmez would be \nquite handy. For wheels, I used a couple old mouse wheels that I had \nkept. It took a bit of work to clean out the middle to allow mounting \nand they are definitely crooked and poorly mounted but they have stayed \non so far.\n \n<\/p>\n\n\n\n

For speed control a L293D chip was used and was soldered up \u201cdead \nbug\u201d style. Without an inverter it does eat up six output pins to \ncontrol the two motors but I figured I had plenty of pins in this \nsituation. Two pins are used to control motor direction for each side \nand a pin is then used to drive PWM for each side.\n \n<\/p>\n\n\n\n

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However, the GM15 motors are really geared a LOT higher than I \nthought there were and the tall mouse wheels really push the speed of \nthe bot beyond usable levels. The balance between enough PWM to move and\n too much while cruising is a challenge. Some better coding would be \nhelpful as Yahmez suggested to maybe ramp up the power to get rolling \nand then settling it down for cruising speed. Something to work on later\n I guess.\n\n\n\n \n<\/p>\n\n\n\n

I designed the chassis to use basic Pololu QTR encoders with \nstriped disk on the wheels. I\u2019ve done this before with larger sensors \nbut not this small. I thought the Pololu QTR-RC sensors would work as \nthey are small and since I didn\u2019t read the datasheet like a fool I put \nthe thing together and could not get output from the sensor. More \nreading revealed that you need to use the library to read the sensor as \nwhat makes them digital is the small cap that must be charged and then \nread using the same I\/O pin. That will NOT work with driving an \ninterrupt pin for encoder reading. I even tried making my own timer \ninterrupt routine to go read the sensors but could not get any \nconsistent output. Since then I have purchased the QTR-A sensors which \nare pure analog but have not tested if they can transition enough to \ndrive a digital interrupt pin. Plus the fact that the wheels are glued \nto the output shafts and the wiring is on the opposite side there is no \nclean way to replace the existing encoders so that part of the bot is on\n hold. \n\n<\/p>\n\n\n\n

Power<\/h2>\n\n\n\n

\n \nPowerwise a 3.7v lipo with onboard electronics for under \/ over voltage \nprotection was mounted on the bottom side. It\u2019s easy to get to and \nreplace in case it bloats from overcharging and tucked up underneath \nquite nicely. However, everything on the bot is 5v so I used a Pololu \nstep up \/ down regulator to turn the 3.xV into 5V. I believe the current\n limits are 500ma but it appears to be fine for my needs. Pretty sure I \ncould not have run a ping sensor along with everything off that current \nbut this thing is too small for such a sensor anyhow. I couldn\u2019t find a \nswitch that was small enough in my junk pile so I just used a three pin \nheader for power and changing needs. I use a header jumper to power it \nup and a three pin connector for the charger. I used a wall wart charger\n that came with a little quad rotor and it appears to have some current \nlimiting in it as well and has charged the battery without issues. The \nbattery is a 240mah LiPo version but driving the speaker appears to \nreally eat up power so run time is not impressive. Fun, just not \nimpressive.\n\n<\/p>\n\n\n\n

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Brain Power<\/h2>\n\n\n\n

\n \nOriginally I really thought I would go with one or more ATiny85 CPUs for\n this build but seeing the ability to mount up a ProMini 328 I changed \ndirection as it is still my favorite Arduino CPU to use since it\u2019s so \nsmall with full 328 capabilities and memory all in a 24 pin DIP. Instead\n of building a undershield or perfboard this time, I simply glued the \nCPU to another little mount I designed and printed that also mounted the\n wheel encoders (that do not work as noted above). I then soldered wires\n directly to the CPU instead of using header pins. Messy but seems best \nat this scale for me.\n\n \n<\/p>\n\n\n\n

Sensors and Stuff<\/h2>\n\n\n\n
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IR Receiver<\/h3>\n\n\n\n

\n\nI added an IR receiver to allow controlling the bot and his \u201cmodes\u201d with\n a standard remote control. Each mode can be selected from the remote \nincluding RC control, autonomous mode, and some special entertainment \ntype of functions. The IR sensor mounted on top of the AtMega chip on \nthe ProMini quite nicely in my opinion. For now I\u2019ve used an existing \nremote from a Toshiba stand alone DVD burner I had in the workspace but \nany remote could be used as it is quite easy to add IR control to a bot.\n I used to think that would be a challenge but with the IR library it\u2019s \nvery simple.\n\n<\/p>\n\n\n\n

The remote is primarily used to change the \u201cmodes\u201d of the robot from \nroam, light seek\/avoid, light track\/hide, \u201cwag\u201d, bark\/attack, line \nfollow, etc. It can also be used to drive the robot around with the \narrow and navi buttons if desired.\n \n<\/p>\n\n\n\n

IR Transmitter<\/h3>\n\n\n\n

\nSince I could not get the encoders to work, that freed up pin 3 that is \nused for the IR transmitter library so I stuck an IR emitter on the \nright rear of the bot. Thoughts are he can eventually communicate with \nSBot or something like that. Nothing is coded yet but maybe later.\n<\/p>\n\n\n\n

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LDR Light Sensors<\/h3>\n\n\n\n

\nSensors are rather simple with two LDR\u2019s for light measurements. Good \nnews is the LDRs work well. Lilliputian can sit still and track light, \nturn away from light, and follow or run away from light. He also makes \nlittle bleepy sounds when he\u2019s not happy with the light balance as he \nsees it. Bad news is my light follow code isn\u2019t overly developed so he \ncan get confused and start spinning in place rather easily.\n\n \n<\/p>\n\n\n\n

QTR-RC Line Sensors<\/h3>\n\n\n\n

\nThe line sensors do seem to work well using the Pololu library and can \neasily detect light, dark, and edges. BUT doing so in a fast enough \nmanner to get a timely response from the platform has been a bit of a \nchallenge so far. Additionally my chassis design leaves some to be \ndesired as the offset wheels make it quite easy for the bot to do a \n\u201cwheelie\u201d when taking off which confuses the front mounted line sensors \ninto thinking it has seen an edge so it stops, backs up, takes off and \nrepeats the loop. Not good. I ended up mounting a small piece of Lego \njewel in the back corner to stop the wheelies helping the edge detectors\n to function.\n\n \n<\/p>\n\n\n\n

Bump Sensors <\/h3>\n\n\n\n

\nWithout sonar Lilliputian is pretty blind so I added a small bump switch\n up front. I can\u2019t remember where these little switches were scavenged \nfrom but they are pretty handy little things that take very little \npressure to turn on making them good sensors for a small bot. I think \nthey were out of some old tape backup drives or something. Without \nwhiskers they are pretty limited but does give some sensing to back off,\n turn and continue on at least.\n\n\n \n<\/p>\n\n\n\n

Light and Sound<\/h3>\n\n\n\n

\nI always like my bots to make a bit of light and noise since I\u2019m easily \nbored so a piezo speaker was salvaged from an old PC motherboard as \nrecommended in the shoutbox and mounted on the rear. A cycling \nmulti-color LED was mounted up front that adds a LOT of colorful light, \nin fact a bit too much so I added code to turn it on\/off via the remote \ncontrol. With the little speaker Lilliputian can play a few songs and \nact out or dance a bit.\n\n \n<\/p>\n\n\n\n

Feature Set<\/h2>\n\n\n\n

\n\n \nLilliputian currently has the following modes and features:\n\n \n<\/p>\n\n\n\n

Roam mode<\/h3>\n\n\n\n

\nNot overly useful but wanders around bouncing off things, avoids black \nlines if the line\/edge avoid flag is set. Line\/edge can be turned on\/off\n with the remote as needed.\n\n \n<\/p>\n\n\n\n

Light Track mode<\/h3>\n\n\n\n

\nIn light track mode Lilliputian sits still and turns toward the \nbrightest light source he can see at the time. If it\u2019s too bright or you\n get too close to him with a flashlight he will back away from the \nbright light making a little noise. Again, in this mode he doesn\u2019t drive\n anywhere forward for light, just sits there.\n\n \n<\/p>\n\n\n\n

Light Hide mode<\/h3>\n\n\n\n

\nJust the normal inverted light seek mode but again sitting still and \nturn away from any light source until he is happily balanced. This \nreally doesn\u2019t mean find the darkest point, just turn away from any \nbrighter light source.\n\n \n<\/p>\n\n\n\n

Light Seek mode<\/h3>\n\n\n\n

\nIn light seek mode, Lilliputian follow the brightest light using the \nfront LDRs for balancing. This works best when pointing a flashlight at \nthe front allowing light control of Lilliputian. He will follow the \nbrightest source he sees and once things are bright enough he will stop.\n If you make things too bright he will back away from the light.\n\n \n<\/p>\n\n\n\n

Light Avoid mode<\/h3>\n\n\n\n

\nAgain standard light avoidance routines, run away from the light. In \nthis mode if he finds a dark enough situation he will stop as well and \nwait for any light changes.\n\n \n<\/p>\n\n\n\n

Race mode<\/h3>\n\n\n\n

\nJust a silly little setup where he counts down with blips and takes off \nat full speed for a second or two. Just like in real racing, sometimes \nhe crashes trying to go too fast. Once done he sings a little tune and \nspins in place having enjoyed the thrill.\n\n \n<\/p>\n\n\n\n

Wag mode<\/h3>\n\n\n\n

\nAnother silly one borrowed from SBot. Just wags back and forth for you.\n\n \n<\/p>\n\n\n\n

Bark \/ Attack mode<\/h3>\n\n\n\n

\nAnother silly little routine from SBot where he drives forward, makes a barking\/noise sound and retreats.\n\n \n<\/p>\n\n\n\n

Line Following mode<\/h3>\n\n\n\n

\nLilliputian is really not well versed in line following yet. He can \n\u201cusually\u201d follow the line but with the high speed, bad code, and having \nto check for IR inputs, etc he can easily miss the line and take off \nrunning away. Even when following the line he is pretty jerky bouncing \naround trying to stay on course. But he can make it around a normal line\n sometimes.\n\n \n<\/p>\n\n\n\n

HokeyPokey mode<\/h3>\n\n\n\n

\n \nApparently he learned this routine from my TED robot I guess. One of the\n most important routines he plays the song and does the moves the best \nhe can. Seems like he is having fun at least.\n\n<\/p>\n\n\n\n

\n