How to make a motor beep?

[jswayze]

Castle Creations (and probably others) modulate something in the motor to make beeps at different frequencies (I'm thinking of the CC Phoneix 25 in particular). Does anyone know how this works? Are they just sending an AC signal to two poles?

I'm trying to find ways to make beeps without using a speaker/buzzer/etc.

Thanks,

Jeff

[Andy W]

Are they just sending an AC signal to two poles?


Yup.

[Mr.RC-CAM]

Are you designing your own brushless controller? Adding the beep feature to an existing ESC would be a serious challenge.

RC-CAM

[Ledbetter]

To put it plainly, the motor does not beep; the ESC beeps.

The beep is a signal that the ESC is in a certain state, for example, "power on" and "armed and ready" typically have two different audio indicators (the number or pattern of beeps is different for each state).

Regards.

[Mr.RC-CAM]

To put it plainly, the motor does not beep; the ESC beeps.
There is no beep device on the popular ESC's. The ESC provides the necessary excitation to make the noise. But, the actual audio transducer is the brushless motor itself.

RC-CAM

[jswayze]

No, no brushless controllers for me. I'm still working on how to make LEDs flash ;)

Ledbetter: the "beep" really does come from the motor. I conducted a very scientific experiment and made the beep with the motor next to my ear, then the ESC next to my ear. Even with the prop noise I could tell it was *definitely* the motor :D

RC-CAM - you might be able to chime in on this... do you know of any other components that will oscillate with enough amplitude to create an audible noise? I found some "audio transducers" (or something like that) at DigiKey, but they're like $.70 each, so I'm trying to go cheaper.

-Jeff

[Andy W]

What are you trying to accomplish?

[jswayze]

Basically I'm looking for the cheapest and lightest way to provide audible indication during a programming cycle on a board. I could use an SMT LED for visual indication, but it may not always be visible, so I'd like some sort of beep.

[Andy W]

Is this board connected to a motor?

[jswayze]

OK... I think this is becoming more complicated than it needs to be.

I wanted to understand the theory behind the motor beep to see if it could be applied to other (non-motor) applications. My application doesn't have a motor, just a PC board with 10 or so components. I was hoping I could use a capacitor, inductor, crystal, I dunno... just something else that would oscillate given the right input signal.

The reason for doing this is to avoid adding a relatively expensive (and large?) audio transducer/speaker/buzzer.

[Andy W]

I think not. There are only two methods to make sound that I am aware of (although I admit I haven't spent much time thinking about this) -
energizing a magnetic coil of some type (coil speaker or, as it happens, the windings in an electric motor)
energizing some other voltage-sensitive tranducer such as a slice of piezoelectric crystal which happens to be bonded to a rigid material
..a

[Mr.RC-CAM]

If this is a small scale effort, with limited production, then a standard piezo xdcr is about as simple (and small) as it will get. Surplus vendors like allelectronics.com have some choices for under $0.30 USD each. Cheaper if you order 100 pcs at a time.

If this is for a consumer high volume design then don't sweat it. Your Far East board assy vendor will install these for about a nickel each.

RC-CAM

[Ledbetter]

Motor beeps itself? You could knock me over with a feather. My Multiplex brushed ESC sounds just like my Palm Pilot. I will, however, bow to superior experience.

Radio Shack carries little piezo-electric transducers if you only need one or two.

[Comatose]

Sometimes you have multilayer ceramic capacitors that buzz or whine in power supply designs. Usually it's not considered a "feature" though.

[gulio]

This forum is way over my head, but here's an article talking about the motor beeping cuz of the esc. I have had one of these esc's and it does beep quite well. very ingenious.

http://www.rccentral.com/article.asp?ATCL_ID=66&PAGE_NUM=222

[Mr DIY]

A lot of controllers use the motor to make the beeps...and actually, it is very easy.

Choose a low PWM frequency between say 8 and 14KHz and simply commutate your motor at a high enough switching frequency so that motor cannot turn. The audible volume is then controlled by the power supplied .. Ie: your PWM duty cycle. You need to play around a bit to find what works best.

Brian

[vintage1]

Quitre right. A motor and a loudspeaker are very similar basically.

Try taking a small motor and connecting it to the output of your hifi. In series with a sensible resistor. (say 4 ohms)

You can hear music on it. Tinny and not very loud, but its there.