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Vibrator motor...
2

Vibrator motor...

Vibrator motor...

(OP)
Hi all,

I have created a little RF transmitter/receiver module (with encoder/decoder). The decoder is the following and of hi quality (R-8PD 4-Bit Decoder IC, http://www.rentron.com/remote_control/Holtek.htm#R8P)

Now, the DataOut of the decoder has +3v when signal is sent by the transmitter. This is ok but if I connect a LED to the DataOut&GND then the LED turns on (good news) BUT when I connect a vibrator motor (http://www.selmag.com.tw/en/p/39-vibrator_coin_type_33.html), the vibrator doesn't activate (bad news).

Since I need to activate this vibrator motor my questions are:
1) Why although the voltage is OK, the vibrator motor isn't acivated?
2) Is it a matter of some extra circuit? What should this circuit consist of and how may I construct it? Any schematic would help so much.

Regards,
Alexis Yannopoulos
Mech. Engineer NTUA, MSc

RE: Vibrator motor...

100 mA maybe?

RE: Vibrator motor...

More like 130 mA for the motor starting current.  But Bob is correct, it is exremely unlikely that your RF module "Data Out" pin will push that much current at 2.5 volts.  Look into Darlington transistors.

RE: Vibrator motor...

Yes, absolutely you will need a transistor to be driven by that output - to run the motor.  Look up an "open collector circuit".

A Darlington will likely be too much voltage drop to work.  You just need a single MOSFET of BJT transisitor that can handle 200mA.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Vibrator motor...

Listen to Keith, he's a lot smarter about this stuff than me.

RE: Vibrator motor...

(OP)
Also, please, if I get one MOSFET transistor, how shall I connect the 3 pins (SOURCE, DRAIN, GATE)?

Regards,
Alexis Yannopoulos
Mech. Engineer NTUA, MSc

RE: Vibrator motor...

(OP)
Last but not least: searching the web, I realised that I will also need a flyback diode? Is this a normal diode? And how is this connected?

I a so confused now.

Rgds and thanks in advnace

RE: Vibrator motor...

As always, I suggest that you get a real electrical engineer on this.  While the suggestions are correct, they assume a certain level of circuitry competency.  

Do you know whether the vibrator current will cause any noise problems for the remainder of your circuitry?  

Do you even have enough power to run the vibrator?

Have you sized the battery sufficiently to not have to change batteries every hour, or whatever?

 

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Vibrator motor...

Take a look at the application sheet listed on your Rentron page link above.  It shows the decoder driving a relay.  Just substitute your motor for the relay coil.  Or, make the circuit as shown and use the contacts of the relay to turn the motor on/off.

RE: Vibrator motor...

BobM3 has it!
That is the very circuit I'm suggesting.

If you want to use that FET as the transistor you can.  Don't bother with the 2.2k resistor if you use the FET.  Or use the 2222 and include it.  If you use the FET the 'source' is grounded and the 'gate' is the control.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Vibrator motor...

(OP)
I bought some resistances, a transistor and a diode to follow the circuit diagram by Rentron and OOOPS! I realised that the specifications state that all PINS give 200mA!!!

So I connected all of them to the vibrator and worked.

Thanks a zillion again

Alexis

RE: Vibrator motor...

That spec is not meant for you to do that with it.

You should proceed with the transistor.  Your setup will possibly soon fail.  

Keith Cress
kcress - http://www.flaminsystems.com

RE: Vibrator motor...

(OP)
May I kndly ask why that?



 

RE: Vibrator motor...

The output transistors have to operate in parallel to pass that much current, and it is likely that one of the outputs supplies a much greater part of the load, stressing it disproportionately (overheating).  Overheating silicon is bad (likely to let out the magic smoke).

RE: Vibrator motor...

Yep.

aware;  That so-called decoder chip is just a PIC microcontroller programmed to provide that functionality.  Holtek's spec just parrots the PIC's normal data sheet.  The 200mA is what you could drive out of 8 pins as you are to limit the current out of any single pin to NO MORE THAN 25mA.  Their warning is that if you somehow had a whole bunch of pins sourcing 25mA each you would exceed and possibly burn out the supply pin bond wire to the entire chip.

You need 120mA to run your vibrator.  That equates to 120mA/25mA = 5 pins.   Are you using five pins that all turn ON at the same time?  If you are not, you are badly stressing the chip.  It will fail.  S o o n.

Hook it up like they tell you to and you won't have any failures and flaky behavior.




 

Keith Cress
kcress - http://www.flaminsystems.com

RE: Vibrator motor...

Now, if the OP would kindly answer...what the heck are you remotely vibrating?

RE: Vibrator motor...

(OP)
It's a communication project that I am working on.

RE: Vibrator motor...

For use in a casino?

 winky smile !!

 

RE: Vibrator motor...

Quote (aware):

It's a communication project that I am working on.
Could you be a little more specific?  What frequency range?  Does the school offer stocked labs to work in and build up a prototype with RF equipment?

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Vibrator motor...

(OP)
Thanks for the reply. I followed the schematics on the datasheet and the vibrator motor works ok.
 
However, I face an issue: whenever the signal is sent, there is a time delay of approx. one third of a second until the vibrator is activated.
Is there a way to minimise or eliminate this delay please?

RE: Vibrator motor...

(OP)
it matters in my case, but anyway I found my fault about the 300ms - it was actually some loose connection that was responsible. Now, after fixing this, the delay is much less and almost unimportant to my project.

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