How sensitive are high sensitive relays? - Electronic Circuits Projects Diagrams Free

avajoe · 14th July 2008, 04:41 AM

I know small electric motors (for example one of the ones you get at radio shack for 5 bucks) will generate power when spun by there shaft from an outside source. Are there any relays that are sensitive enough so that they could be hooked up to the motor and than trip the relay when the motor spins at a low rpm?

audioguru · 14th July 2008, 04:52 AM

I doubt it. An electric motor must be spinned fast to make enough voltage and current to (power) activate a relay.

kchriste · 14th July 2008, 05:40 AM

Depends on the motor, relay and finger strength. You can get some pretty sensitive relays. How does 3V@17ma or 1.5V@33ma sound:
http://www.mew.co.jp/ac/e_download/c...ch_eng_txs.pdf

Externet · 14th July 2008, 05:43 AM

Hi.
From the relays I have and used, the most sensitive is the Teltone M-949-01; works with 20mA.
If your spinning motor can generate such at the speed you spin it, it will work.
It is not easy to find lately; seen it at some surplus stores years ago.
Miguel

Boncuk · 14th July 2008, 11:57 AM

I suggest trying a small unipolar stepping motor, e.g. a floppy disk drive stepper for the read/write head. Without any external circuitry in can drive an LED with just a little twist on the shaft. Using rectifier diodes and connecting the outputs parallel you should get reasonable current to activate at least a reed relay.

Boncuk

avajoe · 17th July 2008, 09:22 PM

Quote:

Originally Posted by Boncuk

I suggest trying a small unipolar stepping motor, e.g. a floppy disk drive stepper for the read/write head. Without any external circuitry in can drive an LED with just a little twist on the shaft. Using rectifier diodes and connecting the outputs parallel you should get reasonable current to activate at least a reed relay.

Boncuk

thats a good idea thanks, Im trying to come up with an old drive to take apart and test it

Boncuk · 17th July 2008, 11:13 PM

Quote:

Originally Posted by avajoe

thats a good idea thanks, Im trying to come up with an old drive to take apart and test it

... and try a reed relay if you want to switch any device. They are normally rated 12mA, which is below the current used for miniature relays (20mA and more)

Boncuk

Sceadwian · 18th July 2008, 06:26 AM

Mind you if such a relay were fed from a Darlington or modest gain BJT it would trigger a 'sensitive relay' on micro amps. Use a resistor/capacitor low pass filter and you can prevent oscillation and provide moderate latching times.

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14th July 2008, 04:41 AM	#1
avajoe	How sensitive are high sensitive relays? I know small electric motors (for example one of the ones you get at radio shack for 5 bucks) will generate power when spun by there shaft from an outside source. Are there any relays that are sensitive enough so that they could be hooked up to the motor and than trip the relay when the motor spins at a low rpm?

14th July 2008, 04:52 AM	#2
audioguru	I doubt it. An electric motor must be spinned fast to make enough voltage and current to (power) activate a relay. __________________ Uncle $crooge

14th July 2008, 05:40 AM	#3
kchriste	Depends on the motor, relay and finger strength. You can get some pretty sensitive relays. How does 3V@17ma or 1.5V@33ma sound: http://www.mew.co.jp/ac/e_download/c...ch_eng_txs.pdf __________________ Inside every little problem, is a big problem trying to get out. Last edited by kchriste; 14th July 2008 at 05:41 AM. Reason: Humour added ;)

14th July 2008, 05:43 AM	#4
Externet	Hi. From the relays I have and used, the most sensitive is the Teltone M-949-01; works with 20mA. If your spinning motor can generate such at the speed you spin it, it will work. It is not easy to find lately; seen it at some surplus stores years ago. Miguel __________________ Abolish the deciBel !

14th July 2008, 11:57 AM	#5
Boncuk	I suggest trying a small unipolar stepping motor, e.g. a floppy disk drive stepper for the read/write head. Without any external circuitry in can drive an LED with just a little twist on the shaft. Using rectifier diodes and connecting the outputs parallel you should get reasonable current to activate at least a reed relay. Boncuk Last edited by Boncuk; 14th July 2008 at 11:58 AM.

18th July 2008, 06:26 AM	#8
Sceadwian	Mind you if such a relay were fed from a Darlington or modest gain BJT it would trigger a 'sensitive relay' on micro amps. Use a resistor/capacitor low pass filter and you can prevent oscillation and provide moderate latching times. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har." Last edited by Sceadwian; 18th July 2008 at 06:27 AM.