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frozen at first start

Posted: Sun Dec 25, 2016 5:13 pm
by bud44750
I just helped my grandaughter build her first meped robot but unfortunately when we first turned it on, all it did was make a few short movements back to the home position and never moves again. If we turn it off and manually move the legs to some extreme position and then turn it on it will move back to "home" and then just buzz and never move again. (manually attempting to move servos off this position meets with wants to be there and none of the buttons on the remote have any affect at all.)

All this is quite disappointing for a 10 year old as well as myself as we took great care to put it together.

disconnection of the servos ,one at a time changes nothing. whichever one is still connected just moves to home and stops, but will not walk etc. i.e. remote has no effect
one servo in particular seems to occasionally get "locked and will not manually move (power off of course) with more than reasonable force...just short of breaking something.
it eventually just lets go and will move under manual effort just fine.

all joints checked and are are freely moving.
what is the 4 wire short cable for? no instructions were offered..assume it was for programming ????

any troubleshooting help would be appreciated

Re: frozen at first start

Posted: Mon Dec 26, 2016 7:17 pm
by bud44750
I've done a bit more trouble shooting and turned up that one particular servo tend to "jam" i.e. it won't move even when forced.( It also gets much hotter than the rest.) It has to be shut off then on and then it will move manually....until it sticks again..... could this jam be confusing the program as when it send a movement command it gets no reply indicating movement has taken place. Though unplugging this servo still doesn't make the others work right. also , when a remote button is pushed does the top red light blink when receiving a command or is there any indication the remote is working? How would I order a new servo?

Re: frozen at first start

Posted: Mon Dec 26, 2016 7:52 pm
by spierce
Hi Bud44750,

I'm sorry for the troubles you're having with your mePed! Out of the box, the mePed is pre-programmed to move all servos to the 90­° position and wait there until further instruction is received from the IR Remote.

When pressing any button on the IR Remote, you should see a red LED light blink rapidly. This signifies that they IR Receiver on the mePed is receiving infrared signals from the remote control. If the red LED is not blinking when pointing the remote towards the robot and pressing a button, you may have the IR Receiver plugged in backwards.

The buzzing of the servos is normal because they are continuously reading their current position and trying to maintain the last position they were commanded to move to. Since the lift servos are bearing the weight of the entire robot, they are continuously fighting gravity and buzz a little bit. This is common and is not anything to worry about.

As you pointed out in your second post, one of the servos may be bad and probably needs to be replaced. Please send your address to and I'll see to it that a replacement servo is sent out to you right away.

As for the short cable included with the kit, it is simply an extension cable that is included with the IR Remote along with an IR LED. You can disregard the IR LED and extension cable. The extension cable is provided only if you would like to remotely mount the IR Receiver. The IR LED is included if you want to further program the Arduino on the mePed to send out IR commands, possibly to other mePed robots.

When you power on the mePed, do all the servos (except the faulty one) return to the same, 90° position?

Scott Pierce

Re: frozen at first start

Posted: Tue Dec 27, 2016 12:14 am
by bud44750
I did some more experimentation tonight and found that the red light does not flash at all when the remote is activated , no matter what button. The tiny "pause "button the top of the unit does delay the signal and I can press pause , move the arms, and in a second or so it resets to the home position. The IR receiver doesn't fit when reversed ( interferes with the main board), if the pins are bent sightly it does fir reversed and a red light goes on,but no light when inserted as per the directions. I even reversed the main board and a second red light blinked but operation did not change. I disconnected the lead to the bad servo but it didn't make any difference in operation. Battery checks good in the remote.

Re: frozen at first start

Posted: Wed Dec 28, 2016 1:48 pm
by goerbear
I’m also having servo trouble. When trying to center the MG90S servos four of the eight units were found either stuck or requiring excessive force to rotate. I plugged in the four that were working and I get no movement when sending commands using the remote.
1.) The “POW” light on the MePed circuit board (item 22) illuminates when the board is switched to “ON”.
2.) The “L” light on the IR Sensor (item 28) blinks when any button on the remote is pushed.
3.) If the four working servos are rotated CW to their internal stop with the power off, they will all rotate CCW to their internal stop when the power is turned on.
4.) The “L” light on the Arduino Nano (item 27) flashes once after pressing the small button. The function of this button is not explained in the manual.
Q1.) Can I get replacement servos for the four units that are stuck?
Q2.) Can you explain why I get no movement from the working servos when I send commands using the remote? Do all of the servos need to be plugged in and working for any of the servos to move?

Re: frozen at first start

Posted: Wed Dec 28, 2016 1:56 pm
by spierce
Hi Bud44750,

It sounds like the IR Remote is probably your issue. Here is a picture of where the Power and IR Indicator LEDs are.
mePed LEDs.jpg
mePed LEDs.jpg (340.21 KiB) Viewed 18147 times
When sitting idle, only the power LED should be lit up. When you press any button on the IR Remote Control, the IR Indicator LED should flash rapidly for as long as you hold a button down on the remote.

There is also a plastic tab at the base of the IR Remote that disconnects the battery from the rest of the circuitry in the remote. The manufacturer places this tab there so the remote doesn't get delivered to the final customer with a dead battery. Here's a picture of the tab sticking out of the remote:
Battery Tab.jpg
Battery Tab.jpg (160.62 KiB) Viewed 18147 times
If you haven't already done so, please remove the tab and throw it away.
Battery Tab Removed.jpg
Battery Tab Removed.jpg (276.94 KiB) Viewed 18147 times
After that, your mePed should start responding to the IR Remote.

If the IR Indicator LED still doesn't flash when pressing buttons on the remote, please open the battery compartment at the base of the IR Remote and verify that the IR Remote battery is installed properly. With the buttons facing down on the table, when you remove the battery tray, the battery's + terminal should be facing up, away from the buttons. There is also a small diagram molded into the IR Remote that shows the correct orientation.

Please let me know if these suggestions solved your issues or if you need further assistance.

Scott Pierce

Re: frozen at first start

Posted: Thu Dec 29, 2016 11:15 am
by bud44750

The unit was purchased as DVRHTHNBD Placed on 09/24/2016 07:32:21

we removed the plastic tab first off, also checked the battery on a tester. When the remote is activated the IR LED does not light at all, in fact it is never lighted ( except for a test when we turned it around in the socket and it did light then but the unit still didn't move with remote buttons pressed. When the unit is turned on, and the" pause" button on the top is pressed, killing the signal to the servos, then if the servos are all moved off home position and the button released, all the servos move back to home just fine....seeming to indicate that the servos as well as the movement circuit is fine. I think the fact of no light on the IR would indicate the IR is the problem or the remote is somehow not sending a signal. We went through it again very carefully and reinstalled all the servos as per directions (basically built it over again to make sure everything was lined up as per the directions but it didn't help.