Testing a servo from a crappy chinese batch made toy!

Hi everyone,
I'm a big noob at all this, but I'm learning fast :0

I have this dancing penguin xmas toy that I have taken the button cables out of and attached to an arduino with a motion sensor so when my toddler walks past it, it turns on and sings and lights up.

Now this toy is about 6 years old and USED TO dance as well but it hasn't for a year (so i didnt screw it up recently with the sensor addition).

I have taken it apart and inside is a perfboard with multiple cables, about 6 capacitors , transitors and resistors.

I have identified two cables going to the servo which have 2 x 104 ceramic capacitors and another black one (haven't checked the power of it yet).

Anyway... I would have thought just putting 5v and gnd to the two terminals on the servo should get it working... however after identifying the positve terminal.. it still doesnt work.

Short answer: Is it buggered

Longer question:
If short answer is "maybe it isn't" - how can i test this to see if the servo itself it working.
If it is, then i might look at the circuit. If you think it isn't... then I'll just give up and keep then singing and LED's working and forget the rest.

Thanks for any advice.

I think some pictures would help us help you.

What makes you think you have a servo? Servos generally have more than 2 wires.

Steve

lkol theres my noobness coming out. ill post a pic :slight_smile: thanks guys
(and as a note - don't waste too much time on this, if its possible to test/fix i will, but its more of a learning experience.)

So In one pic u can see the purple cable has come off.
That just happened somehow but it looked firmly connected before. That connects to a point just near where the red power goes in (positive to the “servo” thing)

Learn how to include pictures:

lols, thanks.
TBH i actually did look but could only find the attach section and the "add image" only allowed a URL.
How do i add them?

There is a tutorial somewhere on the forum. You post with attachment only, copy the link and modify the post including the links.

Thanks :slight_smile: ill check it out

Robin2 created a post to describe the process.

gangel77:
I have identified two cables going to the servo which have 2 x 104 ceramic capacitors and another black one (haven't checked the power of it yet).

Anyway... I would have thought just putting 5v and gnd to the two terminals on the servo should get it working... however after identifying the positve terminal.. it still doesnt work.

If short answer is "maybe it isn't" - how can i test this to see if the servo itself it working.

the 2 100nF capacitors are most likely to prevent radio-disturbances, the electrolytic capacitor across the poles is a good indication of the polarity the purple wire should be the positive since i recognize a grey stripe on the other side indicating minus. The dancing mechanisms usually involve a circular motion that becomes a back and forth and exactly there the whole thing might be jammed. You'll have to disassemble further, you may also find a clear indication of the power and voltage required (that batteries that used to power it are also an indication. and it might be good to measure the amperage before connecting it to power-supply that might not be big enough.

The active mechanical component is not a servo, it is a brushed D.C. motor, with some sort of gearing and/or cam mechanism. As mentioned, the three capacitors across the brush terminals are to reduce electrical and radio noise.

Thanks guys,
Ill take it apart further and see what's up with it.

I have been testing with the arduino connected to mains power via the jack.

How could i jus test to see if it is working (if i find something?

Positive to to the purple terminal and neg to the grey?

Ok - Update:

I took the piece apart back to just the motor. No issues in there, greased and all looking fine.

Tested:
Working now with +ve and -ve to the purple and brown cables.

Put a bit back together - intermittent

Put all back together - sporadic./not working.

I believe just moving it around is causing this rather than the gears jamming now.

So testing it and it is shorting out. (eg. +ve and -ve cause the arduino to turn off).

I also tried running the program via the power and it starts to play and then shorts out, turns on, shorts etc.

The shorting and restarting is when the power goes to the motor to start the dancing.

Soo.

I cant see any crossed wires here on the outside specifically, however there are the 3 capacitors.

I do have others of these.. Should i just replace them all and solder it a bit better?

You should not power the motor straight from the Arduino, Period ! Induction could fry the Arduino beyond repair. there is not even a reverse diode on the motor. The chance of the ceramic disk capacitors being broken is extremely small, they hardly ever break, the electrolytic capacitor is there to get the motor spinning first up, it's probably fine, unless you've had the polarity reversed once. The resistance of the motor is anyway tiny, so much so that a multimeter may see it as a short. For testing power it from a separate powersupply with an abundance of power (watts ! not volts) if it keeps stopping, get rid of it...

When a motor is not spinning (is stalled) it need a lot of current. Power source strong enough may even destroy the motor when stall current is supplied for longer time.

K thanks.
So it’s probably dead.

Is current of 3 AA batteries just 4.5v so Arduino 5v should be the same though?

4.5v is not current, current is measured in Amperes, the batteries provide 4.5v but the current is not specified. The Arduino provides 5v but the regulator will switch of when to much current is drawn making it to hot. the Arduino will reset the motor will stop etc.. The max current that the regulator of the Arduino can provide is dependent on the type of Arduino you are using. If it goes for a while, it probably goes given enough power. If it is fried it doesn't go at all anymore. I think 5v is fine, but not from the Arduino !!

K so I’ll try with the normal batteries and just se did it works.
If it doesn’t then it’s stuffed