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floodhound's blog (11)
Other ways to think
A current traveling in a conductor whose impedance is greater than zero, will produce a potential across it.
The circuits power supply ground will be closest to 0v. 0V is in fact only a common point that all other points can referenced from.
June 25th 2011
Today I did some rudimentary programming and circuit testing for the security mode of my rover. In the video you can see the various frequencies that the alarm will modulate within. It’s running with 5volts to keep the decibels down. The final version will be much louder in fact ear piercing I am sure. Circuit board is still being delayed because I can’t make up my mind on various details. A peek at the schematic you say…
here is my youtube link over at sicklabs https://www.youtube.com/watch?v=49IV2Mzf-C8
Performing some crude test tonight. Pan, tilt, Battery, and power management were completed.
The pan and tilt was a essential test to extract the “range of mobility”. The sensor deck needs to read analogous data, if that is that the correct word to use in this setting. And in doing so it must track without hitting the deck lid. I will attempt to move the base of the robot as the sensor deck approaches these outer limits.
Battery and power management works flawlessly, nothing went boom! That said and without out getting excessively technical (the ambient is working its subtle yet effective magic) I am pleased with the results so far.
Design update: engineering a circuit to monitor battery levels. Not critical for the robot but may become valuable when I inoculate it with code, bringing it to life…
Ah almost forgot, check out my youtube page "Sick Labs "and see for yourself.
Engineering a robot while on ambien.
This design, this curse, is finally starting to gain momentum. I am sourcing parts for my robot and given I know what features I want to implement, part sourcing is still tough. I am loosing my mind trying to stay awake and thumb through data sheets as fast as possible. All while it makes since, while the mind is fresh. You could spend a lot of cash on a particular part, or change design and it may end up costing less. But never over look the old “caught up in this chess match of, well this part is cheaper, but this part is better.” Often I find myself designing a circuit using cheap parts only to find out that the cheap parts need supporting parts that cost too much. This is daunting and could be a career all in it self.
Nevertheless I press on. I found a perfect IC to backbone my H-Bridge. The A4904 automotive full h bridge MOSFET driver turns out be be a complete unit for driving N-chan Mosfets and particularly N-chan Power Mosfet. I get all this for $4.27 in a 24 TSSOP package. I think I will ask for 8 samples from Allegro. So this may end up free of charge.
pointer for the nerds. On datasheets the words “automotive” typically means that the device runs on ~ 12 volts. This is valuable to know as it makes searching for mosfets and other IC so much easier.
Starting to doze out I want to mention some last details that are my notes:
Circuits that are complete or partial complete
Bat-led-cell 12V 2000ah
Switching power supply 3.3v core I
Switching power supply 5v core II
5v precession reference core III
2. H bridges
4 GPS 128 satellite tracking
4 DC motors
1 pan & tilt
I/R sensor array
Gas sensor, monoxide, co2 etc.
Time clock calendar
Television ir transceiver
This circuit board design is more difficult that I imagined. I find it very difficult to engineer something for myself than for others. I just want it to be perfect and I am slipping.
- 12Volt 7,0Ah Nonspillable SLA battery from TYSONIC
- Lynxmotion A4WD1 v2 base kit. https://www.lynxmotion.com/c-111-no-electronics-kit.aspx
- 2 Servos Htec HS-465MB (don’t habe my glasses so that M counld be an N)
- Custom sensor housing (Aluminum sheet metal with 2, twenty fice degree bends)
- 12V mini automotive alarm a.k.a. siren. Great for watch dog mode.
Problems so far with inventory:
- Battery is a tad bit too large;. Ill need to modify the chassis by cutting some aluminum sheet metal then bending.
Progress report 3.17.2011
I finally have a chassis, motors and wheels for this robot. The next step is to design a circuit. I have some things in mind and one of them is the ability to map environments. This will include Temperature, Humidity, and Location. I want to also provide micro SD memory (4Ggis), wireless link to a PC (perhaps a router or a cell phone), distance sensing, GPS, time, and motion detection.
I am that guy people run to when the internet is not working, or they cant find a network printer because a graphical environment operating system is too complicated. The guy you want to have around when your porn habit has caught up to you and your computer is no longer responding. I am exactly that over caffeinated, fast talking, wont listen to you talk cause I know what your going to say before you finish speaking guy, that you go home and tell you're unsatisfied wife about. I am hated because I don't have the time or the attention span to discuss the undemanding details of your life with. I am loved because I retain no fear in the arena of technology. I seek and solve problems at an alarming rate. Bottom line, I make my company dead hard cash and a lot of it, so I must be tolerated.
I do have a challenge at my job because computer repairs and networking issues are boring to me. I design PCB's (printed circuit boards), write programs, and engineer electronics circuits all while trying to keep my ego from getting out of line. Some things I have deigned are being used by many prominent places. NASA has one of my instruments, as well as MIT and other institutions that have an audience of exceptionally smart people. This makes my already inflated ego especially exaggerated for some reason. I reflect now and again and find that my job is parallel to the super bowl. I am in the technology super bowl and I am leading by a large margin. Problem is - they are all German soccer fans (inside joke for the staff here at suck-o). I love my work but I cant tell anyone about it. Its not that its top-secret stuff, its the undemanding actuality that no one I know has a clue of what I am talking about. When I say "hey I used a cunningly simple concept today. I employed a rectifier IC as a EMF suppressor saving the design cost of $1.50 per board." People just shake there heads and walk by. Its depressing for me, the over caffeinated, egotistical, bi-polar, that I cant find someone to correlate these clever solutions with. At the same time its exhilarating because I am winning the super bowl.
So about 2 days ago I received the wheels that I ordered. I knew they were going to be small but man they just wont fit this frame that I had made. This is always my problem, being married my wife wont allow me to spend a lot of cash on "toys" as she calls it. Thus said, I have to find parts from old or broke systems and often that make its difficult for me to get projects going. This specific project will have to wait for wheels. Next time I see a kid in my neighborhood playing with an RC toy - if its got good wheels on it, I am going to run up and take it from them.
Nevertheless I have a new and better idea. I am still going to make a robot just in a smaller frame and using a smaller battery. Stay tuned...
Today I started to build the chassis of the robot. One small hurdle that could not be avoided was the size of aluminum sheets that I could use / obtain. The 12” by 12” sheets of metal heavily influenced the overall size and look of the bot.
I cut the side pieces out using a band saw and filed down the edges. Finishing up the clean look was done with a countersink tool. This way the screws will set flush on the exterior. For the battery pan I measured 12” x 7&7/8”. This allowed for a 1/16 inch bend allowance on each side. The bends were wrapped up using a finger break. The total demissions for the battery pan are 12” long by 6” wide. I am installing the mini siren and you can see in the pictures that there is plenty of room for other goodies.
This week the wheels should arrive and I will be able to make the hubs on the mill. I am already thinking of colors and programming ideas…
Today I ordered some wheels for that robot that I am finally going to start and hopefully finish. I grew tired of waiting for parts and went ahead and paid for them. I have also continued to accumulate several other parts over the last year and think that I can begin a solid project with various features.
The motors are 6 mm shaft 12 Volt gear heads and if I recall correctly they are 400 to 1 ratio. In my experience its better to have a lower speed robot with a ton of torque.
The processor running the robot will be two P8X32A-Q44 running at 80 Megahertz and for programming memory I shall employ the 24LC256. The i2c bus runs up to 400Khz so boot time will be quick not that matters on this project. For extended memory I am considering a flash memory card as used in cameras or simply a Bluetooth connection to my PC. Both have issues that I need to consider before any decision is made. Since I have already designed the circuit boards the flash card option will require some trace splicing and hacking, a not so professional printed circuit board approach. The Bluetooth option is already ready on the circuit board but will need some fancy soldering that I just don't like to do. It takes a lot of time to pump the solder on each pad using a syringe and working under magnification.
The frame of the robot will be made of aluminum sheet metal that is about 8 mm thick. It has to support a fair amount of weight proportional to size so aluminum was chosen for obvious reasons. The heaviest item is the battery. I decided on a small motorcycle type battery, a non-spill sealed 12V 7.5Ah rechargeable. The size is 5.9"L x 2.6"W x 3.7"H and weights 5.6 lbs. It should give for some good run times. We shall see...