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81
Misc / Re: what is this white box and arm called?
« Last post by apexstag on April 05, 2016, 01:18:48 PM »
thanks for the reply, when i search repetitouch it just comes up with an app, i'm not after an app rather the robot/motor device with the repeating action. could you get a link to the ebay ones you've seen?

thank you
82
Misc / Re: what is this white box and arm called?
« Last post by johnnywheels on April 05, 2016, 11:55:06 AM »
hey I am helping my kid design a small tech project for school, and he is making something to show how robots can do repeatable tasks really easily and don't suffer from boredom or breaks as humans do.
He wanted to show this with something similar to this - sad I know using this to play a game but this is the principle we want to get across. can anyone tell me what that unit might be called/where I could buy one from? I don't want to spend shed loads on full robotic arm! we are going to build it up with lego into a person :)



https://www.youtube.com/watch?v=Pxn9p_Yqg2U

There's a device called a RepetiTouch, but that can be pricey.

I've seen others on e-bay that range from $35-$60 depending on the seller.

Good luck!
83
Misc / what is this white box and arm called?
« Last post by apexstag on April 05, 2016, 09:22:05 AM »
hey I am helping my kid design a small tech project for school, and he is making something to show how robots can do repeatable tasks really easily and don't suffer from boredom or breaks as humans do.
He wanted to show this with something similar to this - sad I know using this to play a game but this is the principle we want to get across. can anyone tell me what that unit might be called/where I could buy one from? I don't want to spend shed loads on full robotic arm! we are going to build it up with lego into a person :)



https://www.youtube.com/watch?v=Pxn9p_Yqg2U
84
Mechanics and Construction / Re: Robot Construction Log
« Last post by FIFO on April 04, 2016, 06:49:31 PM »
    I have finally identified and fixed the problem. Both the manual and automatic programmers put the 8085 into reset when they are being used to write to the 8155s. When 8085 processor is in reset, it tri-states the data/address bus, and the control lines, including the read (active low) line. I assumed (incorrectly) that the 8155 peripheral chips would see the tri-stated read line as a high, and so I did not bother to have the programmer tie the the line high when it was being used to write to the 8155s. Since the tri-stated read line was actually seen by the 8155 as a low, the 8155 pushed its stored data onto the bus, while at the same time, the programmer was pushing the data it wanted to write to the 8155 onto the bus. This bus contention made it impossible to write to the 8155s, and thus program the robot.

    After I figured this out, I tied the read line high when using the manual programmer, and loaded a short program into the robots memory, to make it stand still. It was successful so I tried to load the same program with the automatic programer, and that also worked. Next I attempted to program the robot using the refurbished 8155s that I though were broken, and they worked. At that point I was feeling pretty stupid, but I was glad that it was finally working.

    I have been experimenting with more complicated programs to test the various circuits on the main board, and so far things have been relatively successful. I was having some issues with the 8085 resetting every so often, especially when main drive motor started, but after adding some decoupling and bulk capacitors, the problems disappeared.
85
Misc / MASSIVE SALE AT SERVOCITY NOW - April 6th !
« Last post by ServoCity on April 04, 2016, 09:11:00 AM »

https://www.servocity.com/
ATTENTION SALE CUSTOMERS: If your order is over $50, our free shipping offer will automatically be applied to your order (not valid for expedited or international orders). Expedited and international orders will automatically have $6.99 deducted from the shipping total.
86
Mechanics and Construction / Rampaging chariots
« Last post by makspll on March 30, 2016, 08:46:25 AM »
I'm participating in the Rampaging chariots event in June. basically they give you a kit, and you have to build a robot, which is then supposed to either participate in robot sumo, tug of war and then in football and an obstacle course race.
here is the construction manual with all the specs: http://www.rampagingchariots.org.uk/construction/rampaging-chariot-manual-2015.pdf
and the rules: http://www.rampagingchariots.org.uk/games/rampaging-chariots-robotic-games-rules-2015.pdf
could someone guide me on what power transmission should we use to get the torque needed to push a 12 kg robot that is pushing aswell, out of the ring.
we also wanted to transmitt the power onto all wheels (4x4 drive)
we also want to add a scoop, front wedge to lift enemy vehicles easilly at sumo.
also maybe adding tank tracks would be useful
could someone guide us ?
87

note the best way to cool this chip is through through the thermal pad on the bottom of the chip, but without making a new board the heatsink on the top is better than nothing, if you still have overheating a small fan can make a big difference.

if you are supplying the board with only a 1.33A wall wart but trying to draw 2A there is a chance you are undervolting the system. basically as you try and draw more than 1.33A the voltage will start to drop. the datasheet lists 8v min for the load supply voltage. i would recommend using a power supply capable of delivering the desired current and adding a fuse if you are concerned about something drawing too much current.

looking at your motor pinout i think you might need to flip the blue and red wires. the motor datasheet i pulled off sparkfun shows:
BLK A
GRN A-
RED B
BLU B-

i do not see the yellow and white wires listed on the datasheet but it is likely these are center taps to the windings so that the motor can be used as a unipolar stepper, this could be confirmed with a multimeter.

I have also heard connecting or disconnecting the motor while under power can fry these chips so that may have been the fatal blow to your chip. Im not sure of the exact reason why this can destroy the chip but a motor is also an inductor so if it is disconnected under power the energy needs to go somewhere this can create very high voltages. also there is current feedback through a sense resistor and connecting/disconnecting the motor may cause issues for the current regulation.



88
Mechanics and Construction / Re: Robot Construction Log
« Last post by FIFO on March 29, 2016, 05:23:20 PM »
    I have been doing some debugging of the programer, and have discovered something very interesting.

    At first I thought that the manual programmer might not have been functioning properly because the supply voltage was too low. I thought this might have been a problem because the programmer is powered by the robot through some relatively long wires, and I thought that the voltage drop might have been enough to drop the supply rail below the tolerance of the ICs in the programmer. I then measured the supply rail at the programer, and while it was low, it was not below the minimum required by the components.

    Even though the supply voltage was in tolerance, because the supply was a little low, I wondered if I increasing the voltage might solve the problem. To test to see if this would work, I removed the main board, (which draws a lot of current and causes the voltage rail to dip a little), and attached the manual programmer. After some testing, it was clear that the programmer was functioning without error. I then measured the supply rail in the programmer, expecting to see a higher voltage, but to my surprise, the rail was only about 30mV higher.

    I now strongly suspect that the main board is somehow interfering with the programmer which is why it is acting erratically.
89
Electronics / Re: Powering Arduino and Dynamixel
« Last post by FIFO on March 29, 2016, 02:58:16 PM »
    If your servos are put under a load that is greater than they can handle, they can be damaged by drawing too much current. To prevent an over current situation from damaging your servo, you could put a fuse inline with it's supply or ground connection, so that if the servo draws too much current, the fuse will blow, preventing damage.

    One annoyance of this setup is that the fuse must be replaced if it is blown. To avoid this inconvenience, you could use what is called a PTC fuse, which unlike a normal fuse, resets after power is removed.
90
Electronics / Powering Arduino and Dynamixel
« Last post by BrokenDynamixels on March 28, 2016, 09:12:29 PM »
Can I use a 12v 5Ah lead-acid battery to power an Arduino and Dynamixel servos? Online I found that they both should be fine going up to 12v, but is there any chance that they will drawn to much current and burn up? Is a fuse all I need to be safe?
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