I am startting this thread to document the build of my rover.
I got the package yesterday and must say I had a fleeting 5 second spell of dissapointment about the small size of the 4WD3 platform. and the flimsy nature of the lexan. On the internet everything looks larger!
10 seconds after that I mmediately realized the smaller kit was a good thing for my intentions.
I began to put it together and realized that this was one well thought out clean and strong design. I became more and more impressed as the evening went on.
I will upload some pics later tonight.
I followed the guide for Assembly (after I realized I should read the instructions) and now have the shell built…
My question is whether or not I should mount my motor controller and batteries inside the rover and what mounting solutiions you guys used on your rovers.
did you guys just mount with stand offs on the underside of the top panel?
I used some small plastic spaces and screws to mount my scorpion. You could use a bunch of washers as well. For the battery you should use velcro to hold it in position. Also, mount everything inside the armour…incase it rains!
GHAAA!!! I been looking at it for like 30minutes+ now and still can’t find the mistake!
Im going to just guess like crazy
Is the mistake that you ordered the wrong gender battery connector?
You took out the screw screwdriver?
You ran out of beer?
I just got my Lynx 6 arm and its going to stay in the box until all my beer is drank ! no drinking while roboteering
I have decided to just buy another micro and write an ethernet server to communcate between the two via TCP/IP sockets. Why fuss about these pins when I can just buy I2C hardware and more micros!
I have more done on the bot but the chassis will inevitably need to come a apart for mounting…
What do you guys do for quick access to your micros? I can see my self needing access to my ethernet port and serial port for program and firmware updates… Would be nice not having to do a bunch of disassembly with the small easily cross thread bolts… (actually my eyes are the crossed problem)
its 12:30 am - I gotta sleep - this robot is starting to rule my life. (yay!!)
Ok, I’ll bite… at the risk of being obvious (I mean other than the beer). You bolted the motors on the wrong side of the motor brackets (3rd picture). Either that, move the aluminum support rails to the other side…
Yes the third hand I picked up finally, it is so handy - same with the power supply ,
I am moving along on my project - I have failed to hijack I2C port pins on my microcontroller… so I am going to buy another micro. This time it will be a Systronix TINI motherboard/micro. It is better tuned to I/O and I get some analog inputs. As far as sensors go I will be go with newer technology such as I2C sensors or One Wire sensors this way I can use the networks and talk to my devices accordingly. My current method has me fighting for more serial ports.
I have a question about wiring my batteries together. I have two 7.2 volt batteries. I would like to wire them in parallel so I get longer capacity. I have a terminal strip I would like to use as a “power header” so I can power all my devices.
Q 1> Can I charge 2 batteries at once if they are connected in parallel?
Q 2> Can the batteries remain connected to my devices while I charge or will I send to many amps down to my devices?
Here are the pics… I still have room for the SSC-32 when I get my arm mounted. but as you can see my micro won’t fit width ways so I had to mount it length ways on the rover. I have to dremel out a space so I could get the ethernet and power outlet to clear for closing it up.
In classic fashion I screwed that up… It fit perfectly - however I neglected to notice that the cables would extend far beyond the ports… I had to remove the polycarbonate to get the power adapter plug to my micro and the ethernet wire for uploads.
I am feeling good about where every thing is mounted. I am most dissapointed in the lack of I/O on my microcontroller but thats my fault for getting the wrong motherboard for TINI. I will get a different one for the second board.
Here are the pics.
I used adhesive velcro to hold the batteries in
I have some extra wire to trim from the motors… always better to be long than short
A 1) If you connect the two batteries in parallel and treat them are one larger cell you can charge them in parallel. I.e. don’t run two chargers, one to each battery, or you’ll get cycling issues. The downside is that generally the packs will charge 1/2 as fast as a single cell. This may or may not be an issue for you.
A 2) It depends on exactly how your power system works. If you have voltage regulators before your components, you’re okay more or less regardless. This is because most battery chargers will charge at higher than the rated voltage of the packs. Note: when peak charged, the packs may have significantly higher voltage too. You won’t send too many amps to your equipment, but too many volts. If you have a regulator, (which can generally take a wide range of input voltage), it will simply regulate the voltage down to an appropriate level. Again, this will seriously slow down the rate of charging as less current will be going to charge your batteries. If you don’t use regulators, it then depends on the tolerances of your equipment. If your charger doesn’t overvolt too much (or your equipment can deal with the higher voltage) then you’re fine. Personally, I would check the charging voltage with a multimeter and double check the specs of your equipment first. It may be okay. Your equipment may have regulators already in them since many bot boards can deal with a range of power sources. Regulators are nice to protect, but unfortunately the best simple switching regulators get about 80% efficiency at nominal load (be careful with the ratings, sometimes they try to trick you). While it is possible to design a high current, high efficiency power supply, that is a project in of itself. I’ll point you at a link: romanblack.com/smps/smps.htm for designing such things. However, unless you really want to dive into low-level EE, you probably will just buy one. All voltage regulators have a minimum voltage drop, too. Meaning if your pack is 7.4V, expect at most around 7.0V from the pack after the regulator. If you use the common 780x series or LM314 (variable) 3-pin regulator to simplify things (i.e. very hard to hookup wrong, blow the regulator) you do lose a lot to heat.
Voltage dividing should technically work, but is highly wasteful and more or less depends on your micro drawing constant current. I’m not familiar with the TINY, but you could very easily under or overvolt depending on what the micro was doing at the time compared to when you calibrated the divider. I won’t advise using a voltage divider for that reason. Yes, you could stiffen the response with diodes, and other tricks, but why when regulators are cheap. Since you need 5V (luckily the most common voltage ), there are many premade linear and switching solutions. Since I thought you needed 6.0-7.0 volts, I didn’t think this was the case.
The circuit you found will work, my only comment is that it is somewhat wasteful since it relies on a linear (less efficient) 7805 regulator. You won’t have any stability issues. Since your bot is battery powered, this is a bigger issue than just generating excess heat since it will shorten run time. Unless your current draw is fairly small (<100 mA), I personally suggest the LM2940. It’s basically a drop in replacement for the 7805 in that circuit unless you need over 500 mA (then just buy more and run in parallel as the 7805 technically supports up to 1.5 A) and gets around 80% nominal efficiency. It’s only slightly more expensive than the 7805, about a dollar and change. I also might suggest making that first capacitor bigger if you find your packs’ voltage varies too much depending upon current draw. Also, be prepared to put a heat sink on whichever regulator you choose. Even 0.5 watts of heat will make a regulator fairly warm.
Looking over the SCC-32 manual, it seems to conflict. It says it will take as low as 5.5. However, then says only use 6.0-9.0V for VL? Basically it has a low voltage drop 5V regulator on it, so I would think that it should be able to deal with a direct connection to the charger so long as your charger doesn’t go above 9V. You still need the power circuit, since the manual derates the regulator to 250 mA for peripherals stating it gets too hot otherwise. Basically, the component itself could do more but it would need a sink. If you look of the part number of the regulator and its a switcher, you might just want to experiment in sinking it. This could range from simply attaching a heat sink to desodering it and remounting it elsewhere with a sink. However, you’re probably just better building a power circuit and not messing with the controller as the probably of breaking something experimenting is rather high.