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Glowing LEDs and 12v motor

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The motor in the disco ball had no load so it was not working hard. The motor turning your statue might be working hard.

The lamp that was connected in series with the motor reduced the voltage to the motor.

Therefore the motor was not hot.

The timing capacitor in the fading circuit charges positive then charges negative so it must be non-polarized.
 
ok, when i buy more components i will get a non-polarized 22uF cap to replace the polarized one.

The motor has no load at the moment as it isnt attached to the sculpture yet ;)

What can i do to reduce the voltage to the motor and replace that Lamp?

heres the specs of the adapter im using if you still need them ...
Model: MKA-120500UK
Input: 240V AC 50Hz
Output: 12V AC 500mA
 
ok, when i buy more components i will get a non-polarized 22uF cap to replace the polarized one.

The motor has no load at the moment as it isnt attached to the sculpture yet ;)

What can i do to reduce the voltage to the motor and replace that Lamp?

heres the specs of the adapter im using if you still need them ...
Model: MKA-120500UK
Input: 240V AC 50Hz
Output: 12V AC 500mA

The motor is a 12VAC which uses 1 Watt at 50Hz, according to your earlier post. The lamp uses 5 Watts. The adaptor is rated at up to 6 Watts (12 volts * 0.5 amperes). So in the disco ball, 5/6 of the current is drawn by the lamp, and the combined load of the motor and the lamp bring the adaptor's output to 12V.

Remember that the adaptor (unless it's regulated) is putting out quite a bit more than 12V with no load (or with a very light load, such as just the motor by itself). So with just the motor on it, the voltage the motor is getting is well over 12V. I suspect that's what's causing the motor to run so hot--it's getting an overvoltage and doesn't like it.

With the limits of my experience here, I'd think that your choices are:

1) Increase the load on the adaptor to bring the current consumption up to around 500mA and thus the voltage down to ~12VAC, which is what the 5W lamp is doing--but this wastes 5 Watts, which is quite a bit; or
2) Somehow decrease the voltage output of the adaptor without wasting the extra 5 Watts. Normally I'd use a transformer for something like that, but in this case I think it would be easier just to try a 12VAC output adaptor with a lower current rating (say, 100mA or so) or even try a 9VAC output adaptor instead.

There are other ways to do it but I'm trying to stay away from them since I haven't got much experience with them and I think they would be a whole 'nother project altogether. :)


Torben
 
i figured this was alot of trouble just to get the motor to work properly so i went and bought this...
**broken link removed**

Now i can keep the whole circuit DC. No doubt it will come with a whole host of new problems :p
 
i figured this was alot of trouble just to get the motor to work properly so i went and bought this...
**broken link removed**

Now i can keep the whole circuit DC. No doubt it will come with a whole host of new problems :p

From the eBay page I think it should work. We'll see when it arrives, I suppose. :)


Torben
 
If you buy an unregulated 12VDC adapter then its voltage might be as high as 18V when the current is low. The fading circuit and DC motor not designed for 18V.
Same problem as before.
 
It's 60 RPM at 12V. You definitely want to drive it with a lower voltage. I would recommend trying 3V first.
 
Yep, your right. Even just using a 9v battery to it, it is noisey and created too much vibration to be used how i wanted it to be :( Im sure i can find another use for it though....

What dc motors should i be looking at then?
It just needs to move about 20-40 rpm, 12v DC, be silent and no vibration, and be strong enough to able to resist you pinching the shaft.
 
If it's 60 RPM at 12V, it's pretty close to 20 RPM at 4V.

It's not necessary (and seldom desirable) to operate a motor at its maximum voltage/RPM.
 
I see.

I have put a 220 resistor infront of the motor to slow it down which has made a improvement to the vibrating it made :)
In addition to that, im planning on making a mount for it to sit on with a small wood frame and rubber bands to absorb the rest of the unwanted vibrations, whilst not letting it move around too much and mess the sculpture up.

and to top it off, ill put a box of polystyrene around it to hopefully muffle the noise the motor makes directly.

its going to take a bit of fiddling and time to make, but i think ill get there
:)
 
Controlling motor speed with a resistor is not a very good way to go as you waste a lot of power. Some sort of PWM circuit would be better. Perhaps someone here has a easy circuit you could use. I will look around later.
 
*Sigh* Ive soldered the circuit all up to find that it isnt working....
The LEDs are not fading again and i am 100% sure the PCB is correct.
Im thinking maybe i damaged the chip while soldering it into place and it has accoured to me that i should of heat sinked it or used a 8pin socket.....

Is there anyway to test the chip to find if that is the problem? :confused: :(
 
Is this with motor connected? Can you try disconnecting motor?
 
Can you define "not working"? Does that mean the LEDs are on all the time, off all the time, the motor is jerking but not rotating. . .or does it just behave exactly the same with power hooked up as it does with no power (i.e. it just sits there like a lump when you turn it on)?

Like Mike said, disconnect the motor and try again.

Check the voltage coming out of the power supply.

Check the voltage at pin 8 of the op-amp.

Double-check to make sure that the LEDs are in the right way 'round.

Look very very closely to make sure you don't have any solder bridges. It's quite easy to accidentally join two pins with a tiny bit of solder which can bugger up the whole thing.

That said, unless there is a dead short somewhere or the power supply is dead, I'd expect that at least the motor would turn, even if the fading LEDs portion of the circuit didn't work.

What are you powering it from now?

I'd say that using a socket is a really good idea unless you expect the circuit to be in a high-vibration environment. It eliminates the chance of solder heat killing an IC and allows you to easily swap in another IC to test.

Hopefully you still have your test prototype circuit set up so you can triple-check the connections.

Do you have a camera which can take good closeups? Cell-phone cameras usually have crap picture quality but a decent digital camera will often have a macro or manual-focus mode which allows you to get quite close. If you can post really clear, close pictures of both sides of the circuit board, perhaps someone will be able to see something you missed.

OK, back to my housework. :)


Torben
 
Sorry, i guess i wasnt bein very helpful with 'not working' lol
The LEDs are 'fading' on, but then stay on and doesnt do anything else. :(
The motor seems fine though and is doing what it is ment to do.

Im powering it from the adapter now which is soldered to the circuit, pretty sure that is fine and isnt the problem as it still happens when i put the 9v battery against it.

I have tested the transistor to see if that is ok, and that seemed fine. (conducts like a diode apart from collector to base where it doesnt conduct at all)

LEDs are not soldered in yet and work, just not fading off again.

What other pin do i put the probe on to test pin 8 of the op-amp?

i think im gonna go over the joints of the circuit to make sure none have broken or anything...
 
Sorry, i guess i wasnt bein very helpful with 'not working' lol
The LEDs are 'fading' on, but then stay on and doesnt do anything else. :(
The motor seems fine though and is doing what it is ment to do.

Im powering it from the adapter now which is soldered to the circuit, pretty sure that is fine and isnt the problem as it still happens when i put the 9v battery against it.

I have tested the transistor to see if that is ok, and that seemed fine. (conducts like a diode apart from collector to base where it doesnt conduct at all)

OK, so it's not the power supply and it's not the transistor.

LEDs are not soldered in yet and work, just not fading off again.

What other pin do i put the probe on to test pin 8 of the op-amp?

Put the black probe from the multimeter on ground and the red probe on pin 8. What voltage do you see?

i think im gonna go over the joints of the circuit to make sure none have broken or anything...

That's a good idea. :)


Torben
 
After resoldering it all it seems to work now.

That was pretty stressfull.... Lol. Still dont know what caused the problem in the first place, all the pins seemed to show some response with the mulitimeter....Ah well. Will just have to solder more carfully in the future :)

But at least i have learnt to make some changes to any future PCBs i make.
First of all i etched the circuit electronicly, so it was a bit patchy and had to go over it wit ha dremmel. And secondly, the tracks and pads where too small, so most of the pad dissapeared after i drilled the holes in it.

But i know better now :D

Thanks for the help guys. Now all i need to do is mount the LEDs in place, solder them on (The right way! Lol) and make the mount for the motor and PCB and then ill be done :D :D :D
 
And secondly, the tracks and pads where too small, so most of the pad dissapeared after i drilled the holes in it.

I don't think anyone that reads this can ever say they did not have that happen. My first boards use to look like utter crud. Good job :)
 
Just use a smaller drill bit.

Don't worry about it, just bridge the solder so the lead is soldered to the traks either side of it.
 
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