Vibrator motor... 2

[aware]

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

 

[BobM3]

100 mA maybe?

 

[btrueblood]

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.

 

[itsmoked]

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

 

[btrueblood]

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

 

[aware]

Thanks for all input,

So a simple MOFSET transistor is all that is needed? Or I need more items to do the job?

For example the MOFSET linked below would be enough for my needs?

http://cgi.ebay.com/LOT-25-MOFSET-N...Electronic_Components?_trksid=p3286.m20.l1116

Regards,
Alexis Yannopoulos
Mech. Engineer NTUA, MSc

 

[aware]

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

 

[aware]

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

 

[IRstuff]

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

 

[BobM3]

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.

 

[itsmoked]

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

 

[aware]

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

 

[itsmoked]

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

 

[aware]

May I kndly ask why that?

 

[btrueblood]

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).

 

[itsmoked]

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

 

[btrueblood]

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

 

[aware]

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

 

[VEBill]

For use in a casino?

;-) !!

 

[MacGyverS2000]

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