Insect Bot -underpowered?

Make:Arduino Bots and Gadgets: Insect Robot -when I load any of the sketches and then connect the 9V battery and remove the USB cable, the speed of motion drops right down - as if the 9V is not supplying enough power. I have tried adjusting the numbers in the sketch e.g. in Walking Forward, but without success.I am using the servo motors you list and a Duemilanove. Do you have any advice on this?
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  • Are the servos still moving, even slowly? If yes, the system is working
    as it should but the motors could use even more power. Servos get
    stronger with more power. Some 9V batteries are not able to give high
    continuous output. You could try the following things to narrow down the
    problem:

    - Check the battery with multimeter to make sure it's OK
    - Check the connections between the battery and the Arduino
    - Use higher quality battery
    - Disconnect one servo. Is it faster now? If yes, motors are actually
    drawing more power than there is available.
    - Using good rechargeable battery with strong output would most likely
    solve this. Although there should be easily enough power in 9V battery
    for the 2-servo walking bot.

    BR,
    Botbook.com
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  • Thanks. Disconnecting one servo makes the speed increase, suggesting that they want to draw too much power.Assuming I can source a more powerful battery, isn't there a risk that the power drawn will exceed the safe maximum for the Arduino which I seem to remember is 40mA?
    (Temporarily I have introduced a second battery, which at least makes the insect walk again!)
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  • Brian Jepson (Editor, Maker Media, Inc.) June 06, 2011 20:31
    Roger,

    Could you post a photo of how you've got everything wired up, with a focus on the battery and servo wiring?

    The 40mA limit is on an IO pin; you can source more power (I can't recall how much) if you're drawing power off the 5v pin. The Duemilanove uses a high quality voltage regulator that should be able to supply 800mA total. The Arduino uses some of that, of course, but there should be plenty for servos.

    - Brian
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  • Brian
    I have taken a photo which I am Adding via the icon on this page. I have disconnected the battery for the photo, as the insect kept flopping around.
    Roger
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  • Brian Jepson (Editor, Maker Media, Inc.) June 08, 2011 22:51
    Thanks, Roger. Everything looks like it was hooked up correctly, but I'm not sure why you'd have trouble getting enough power. Have you tried measuring the current in the circuit? See the Measuring Current section at about 5:40 in this tutorial: http://blog.makezine.com/archive/2011...

    This tutorial has a section on measuring current: http://www.sparkfun.com/tutorials/202

    It would be interesting to see how much current the servos are drawing.
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  • Brian: thanks. I read both articles and as a result put my meter to read 10A. I connected it at the 5V Arduino output i.e. in the top red line of the circuit on p.65.
    Experiment 1: USB connection
    (a)both front and back legs running. Current 0.32 to 0.62A, the flucutation occurring as the legs went side to side with a period of less than a second.
    (b) back legs only (I unplugged D3). Current was 0.24 to 0.37A as the legs went through their cycle.
    (c) front legs only. Current = 0.17-0.25A
    Experiment 2:9V battery connection (new battery Duracell Plus i.e. not rechargeable)
    (a), (b) and (c) as above. Cycle time about 3s.
    (a) 0.01-0.4. The 0.01 is when the legs are stationary.
    (b) 0.21-0.34A
    (c) 0.15-0.26A
    Rather oddly, at the end of this at started trying to make some voltage measurements but then the insect ran at much reduced speed (and correspondingly even slower when I switched to battery!). So I removed the meter completely but the speed did not recover.
    I am awaiting a rechargeable battery in case that is the problem.
    Regards
    Roger
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  • Could you try one thing. Connect the battery red straight to Arduino VIN and black to ground (GND). Does this change anything?

    BR,
    Kimmo
    Botbook.com
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  • Kimmo
    Yes, it is faster when I do that, about 50% faster I guess, but nothing like as fast as when it gets its power from the USB.
    Roger
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  • No it isn't. I now have a rechargeable battery which I am charging up to try.
    Roger
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  • I now have tried the rechargeable battery but it makes no difference. So where do I go from here? How can I get more speed out of the sketch? Changing the 150ms delay between steps does not make any visible difference.
    Regards
    Roger
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  • Can you tell me what's the exact combination you are using?
    -Arduino Duemilanove?
    -Code: Walking Forward?
    -Servo brand and specifications?
    -rechargeable battery specifications, mAh, discharge rate, volts?

    BR,
    Kimmo
    Botbook.com
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  • Arduino Duemilanove
    Walking Forward
    Servos: Sparkfun ROB 09064 sourced from www.proto-pic.co.uk as PPROB 09064, brand=Sparkfun.
    •Continuous 360° rotation
    •Rest point adjustment
    •Operating voltage: 4.8-6.0VDC
    •Top operating speed: 60-70RPM (4.8-6.0VDC respectively)
    •Torque: 3.3-4.8 kg/cm (4.8-6.0VDC respectively)
    •4 plastic gears + 1 metal gear
    •Double ball bearing
    Datasheet link is back to Sparkfun which shows the manufacturer's datasheet.
    Batteries: At first I tried a non-rechargeable Duracell Plus 9V battery. Alkaline MN1604. Duracell website shows a wide range of discharge rates depending on resistance of circuit.I can't see the energy storage but maybe the clue is in the name "1604".
    I then switched to a rechargeable: UniRoss 9V. 170mAh.No discharge information on the website.
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  • Thanks! Now I think I know what's wrong.

    The most usual type of servo has limited rotation. They are used when you need to turn the motor to specific angle. You are using continuous rotation servos. They are suitable for example wheeled robots such as our soccer bot.

    ROB 09064 has limited rotation http://www.sparkfun.com/products/9064
    Is your servo maybe something else than ROB 09064?

    BR,
    Kimmo
    Botbook.com
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  • I have just phoned the supplier who confirmed that this (the 09064) is not a continuous rotation servo.
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  • Brian Jepson (Editor, Maker Media, Inc.) June 13, 2011 16:25
    Roger, sorry to keep asking you to take photos, but could you post a closeup photo of the servo showing the label? I'd like to confirm that you got the part you actually ordered.

    I'm on the road right now, but when I get home, I'll see if I can build the bot using the exact parts that you're using and see what results I get. While we were working on the book, we had a tech reviewer build the bot, but I'd like to give it a whirl myself to make sure.
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  • There are no markings on the servo whatsoever. Maybe I am going to have to order the servos from Sparkfun just to check, but rather than spend the money at the moment, I will wait for you.
    Roger
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  • Brian Jepson (Editor, Maker Media, Inc.) June 14, 2011 16:18
    Hi Roger,

    I did think of something you can try. Can you skip ahead to Chapter 8 and try out some of the continuous rotation servo examples, such as fullRotation.pde on p206? If the servo behaves as described there (rotates clockwise, holds steady for a second, rotates counterclockwise, stops, and then repeats), then you might have been sent a continuous rotation servo instead of a standard servo.

    - Brian
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  • Brian
    I have just tried this. P.206. The (front legs) move about 10degrees to the insect's left, pause briefly, go back to centre, then to right, back to centre and so on. The cycle time is about 4s. As I said there is no "rotation", just an approx. 10degree rotation. I guess this angle is much less than with a continuous rotation servo?
    Regards
    Roger
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  • Brian Jepson (Editor, Maker Media, Inc.) June 17, 2011 13:06
    That sounds like the right behavior for a standard servo--they move to specific positions rather than spin continuously. With a continuous rotation servo, you get a rotational speed rather than a movement to a specific angle. I've got the parts on order for this and will report back soon. Thanks for your patience with this project!

    Regards,

    Brian
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  • Brian
    I have tried the insect again: with USB power and then 9V rechargeable battery. I must say that I get better results for this battery than the non-rechargeable (this time!). I have videoed the insect on its back with the two power modes. Note the different movement patterns and the higher throw of the front legs in the battery-powered version.

    I uploaded them to You Tube under the following titles:
    USB powered:

    robot insect usb powered on its back

    battery powered:

    robot insect battery powered
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  • Brian Jepson (Editor, Maker Media, Inc.) July 05, 2011 00:15
    Thanks, Roger. Sorry about the delay, but my servos arrived while I was traveling. That looks much better, to be honest!

    Let's see if I can put some links in the post so Tero and Kimmo can find them easily:

    https://www.youtube.com/watch?v=sUUYtl...
    https://www.youtube.com/watch?v=FKYcm5...

    It looks like the motion you're getting here should be sufficient for the bot to move around; is it able to walk OK?

    Thanks,

    Brian
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  • Brian
    Thanks. I have tried again with the insect connected to USB and then only connected to the rechargeable battery. The insect walks well with the USB connection but not with the battery - it falls over...........I have videoed both uploaded to YouTube.
    https://www.youtube.com/watch?v=GeMPKd...
    https://www.youtube.com/watch?v=jRz523...
    Regards
    Roger
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  • Hi Roger,

    It seems that your insect's legs are not spread widely enough. USB cable gives weight for the back of the bot keeping it down. Bend the legs so that the center of gravity is lower and legs are so wide that robot does not fall even if you push it by hand from the side.

    BR,
    Kimmo
    Botbook.com
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  • Br
    I have now spread the legs as suggested. The aim is to get the insect to walk under battery power. The speed and "gait" of the USB powered insect are OK, but the battery-powered version is poor. I have videoed these so that you can see where I/we have got to.
    USB connection: OK performance
    https://www.youtube.com/watch?v=zjpZej...

    Battery connection: relatively poor performance
    https://www.youtube.com/watch?v=KdR8vQ...
    Regards
    Roger
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  • I wonder why your servos make just a few moves and then take a break. I have build many walkers with different servos and Arduinos, and never had that kind of problem. While walking, servos should constantly move from left to right. What happens if you hold your bot in your hand upside down? Do servos still take breaks? Can you make one servo move from side to side without breaks?

    You can also try a different approach. Try this code without servo.h.

    int servoFrontPin=2;
    int servoBackPin=3;

    // pulse length for servo control in microseconds (1 us = 10**-6 s)
    int centerPos=1500;
    int frontRightUp=1200;
    int frontLeftUp=1800;
    int backRightForward=1250;
    int backLeftForward=1750;

    void pulseServo(int servoPin, int pulseLenUs)
    {
    digitalWrite(servoPin, HIGH);
    delayMicroseconds(pulseLenUs);
    digitalWrite(servoPin, LOW);
    delay(20);
    }

    void moveForward()
    {
    for (int i=0; i<=5; i++) {
    pulseServo(servoFrontPin, frontLeftUp);
    pulseServo(servoBackPin, backRightForward);
    }
    }

    void setup()
    {
    pinMode(servoFrontPin, OUTPUT);
    pinMode(servoBackPin, OUTPUT);
    }

    void loop()
    {
    moveForward();
    }

    BR,
    Kimmo
    Botbook.com
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  • BR
    Yes, it is the same in my hand (an earlier video showed that).
    At the moment I can't run the previous WalkerForward sketch: I get an error which according to the Arduino website is difficult to solve.
    The error and comment from Arduino is:
    avrdude: stk500_getsync(): not in sync: resp=0x00
    If you get the following error message "avrdude: stk500_getsync(): not in sync: resp=0x00" that means that the Arduino is not responding. There are literally dozens of reasons this could be.

    Check the following:

    If you have a NG Arduino, did you press reset just before selecting Upload menu item?
    Is the correct Serial Port selected?
    Is the correct driver installed?
    Is the chip inserted into the Arduino properly? (If you built your own arduino or have burned the bootloader on yourself)
    Does the chip have the correct bootloader on it? (If you built your own arduino or have burned the bootloader on yourself)
    Note that it is nearly impossible for anyone to debug this, as there are so many possible issues. Try everything.

    I get the same error even with another Arduino board, which is puzzling. So until I can solve that, I won't be able to try your proposed sketch.
    Regards
    Roger
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  • I have sorted out the error and have now tried the new sketch. The result with the USB connection is excellent but with the battery, the insect is hesitant. See videos:
    USB:
    https://www.youtube.com/watch?v=uMLmYm...
    Battery only:
    https://www.youtube.com/watch?v=5rxbNv...

    Regards
    Roger
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  • OK, so the battery is the only problem now. It might be that servos are drawing more juice than your battery is able to give. I would try two things:

    1. Connect battery to VIN and GND instead of DC power connector.
    2. Make sure that your battery has suitable discharge capacity.

    For my last battery powered project for example I used DualSky 1300 mAh 30C 2s1p 7,4 V battery. What do all these values mean? 1300 mAh (milliamp hours) tells about battery capacity. Higher value means longer running time. 30C is the discharge capacity for one hour. In this case 1300 mAh * 30 = 39000 mAh = 39 Ah. 2s1p means that battery has two 3.7 V cells in parallel. So together they give you 7.4 V. 7,4 V is of course the output current. Recommended input voltage for Arduino Uno is 1 7-12V.

    Always use strong batteries carefully and read the manual. Short circuit can lead to heating, fire or even explosion.

    BR,
    Kimmo
    Botbook.com
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  • 1. Connecting to VIN and GND made no difference.
    2. I can see now that the type of rechargeable battery is in a different league. I have found a supplier for the DualSky battery you use but am waiting for the supplier to tell me what else I will need i.e. the model of charger and a "balancer"(?).
    Also a fireproof bag?
    Regards
    Roger
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  • BR, Kimmo
    I have been in contact with the local (UK) supplier of DualSky batteries and find that although the battery only costs £10.20, the charger and balancer are expensive - and I also need various connectors: the total cost would be about £70 i.e. 79euros, so I am holding back in case I can think of a cheaper solution to the battery problem.
    I have now had chance to look at the sketch you sent me which avoids #include and see that it is very different from the original. So how do I change the final sketch?

    Regards
    Roger
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  • Brian Jepson (Editor, Maker Media, Inc.) July 15, 2011 14:54
    Roger,

    I wonder if the least expensive option is to determine whether you have the same servos we are using. I believe you confirmed that the vendor specified these as being sourced from SparkFun, but I am concerned that you didn't find a label on them. Mine has a label on it, TowerPro SG-5010, which you'll also see in the photo on their product page: http://www.sparkfun.com/products/9064

    If your servos don't have any identifying marks, then I think there is a good possibility that it's a different servo than what we're expecting, which could explain why it's drawing too much current.

    As regards the different code example that Kimmo posted, you can open a new Sketch in Arduino, paste in that code in its entirety, and upload the sketch to the Arduino.

    - Brian
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  • Brian
    Although the servos I received do not have a label, their image on the website of the local supplier is identical to Sparkfun (www.proto-pic.co.uk). I have emailed Proto-pic to clarify. I could of course buy two directly from Sparkfun - but are you sure they work from an "ordinary", non-Lipo battery?

    Regarding the sketch, the aim is to have a complete insect with detector, so I would need to get the sketch called walkerForwardcomplete.pde working. Wouldn't that mean a complete re-writing of the sketch? Maybe simply sourcing two new servos from Sparkfun (if they don't need a Lipo) might be the most effective solution?
    Regards
    Roger
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  • Brian Jepson (Editor, Maker Media, Inc.) July 15, 2011 17:14
    Until today, I hadn't built it myself (I had a tech reviewer build it though). But I did just now, and I'm getting great movement with 9v going into the VIN. This is just running the walkerForward sketch, and my robot is a little unbalanced (I attached the Arduino and battery a little hastily): https://www.youtube.com/watch?v=-fPgxW...

    I think it might be worth sourcing two new servos from SparkFun, but I'd suggest one other thing first: if you have four rechargeable AA batteries (1.2V x 4 = 4.8V), I think you can use those instead of the 9V battery, but plug them into 5V rather than VIN so that they bypass the voltage regulator and don't get stepped down. For this reason, it's important to make sure you're using 1.2V batteries, otherwise you would be sending 6V into the Arduino which wouldn't be good.

    You'll need a battery holder for them, but those are relatively easy to find.

    Cheers,

    Brian
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  • Brian
    I have had a go with 4.8V plugged into 5V. (I had to modify a 6 battery holder. The four rechargeables gave 5.6V so I had to introduce a potiometer to reduce the voltage to 4.8V). I checked that with the USB connection, the insect marched forward trying to wreck everything on my desk. With the 4.8V it just twitched. I could not film it because I would have needed four hands......

    The UK servo supplier assured me that the servos were the right servos "Yes these are the SparkFun Servos" but I will order two directly from Sparkfun.

    Before I "invest" in "LiPo technology", can you confirm that the 9V battery you used yesterday is a LiPo or is it a Ni-MH: put another way, would your genuine Sparkfun servos work with a rechargeable Ni-MH?

    Regards
    Roger
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  • Brian Jepson (Editor, Maker Media, Inc.) July 16, 2011 13:18
    Thanks, Roger. This test was with a fresh alkaline battery. I don't have any rechargeable 9Vs with me.

    Cheers,

    Brian
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  • Brian
    Thanks. So we are homing in on the servos. I have ordered two from Sparkfun - that should eliminate that source of doubt. I will hold off from ordering a LiPo battery and charger for the moment.
    Regards
    Roger
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  • I’m pleased
    1
    See https://www.youtube.com/watch?v=PmK9uT...
    I received the servos from SparkFun which are TowerPro SG-5010. These are different from those shown on p 55 of the book, which is of some concern, but they work very well.
    I will now continue with the project...........
    Thanks.
    Regards
    Roger
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  • Brian Jepson (Editor, Maker Media, Inc.) August 11, 2011 17:07
    That's great news! Those are the ones I tested with as well. The photos in the book were taken with parts that the authors sourced in Finland, so we tested things with parts in the US but we didn't update the photos because the authors' photos were so awesome.
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