Relay Drive without using transistor

[SR19]

Hi ,

I need to drive a relay with the capsense output which is active low..any other way to drive relay without using transistors?

Thanks

 

[throwaway18]

You are taking about a capsense device from Cypress semiconductor?
A little device that detects when a person touches a contact, a switch without moving parts.

The datasheet says that a GPIO pin can do 20mA in low state. There are reed relays that
can operate with 10mA. The contacts of reed relays are not for high voltage or high current, you
could use a reed relay to control a larger relay but obviously it would be better to use a transistor.

There are solid state relay modules that will switch high voltage/current with a low control current,
often 1mA or less, but they have transistors inside so that still counts as using transistors.

 

[SR19]

Hi,

Thanks for reply..Yes im using Cypress capsense IC. My design has 13 buttons. Some of these buttons have to drive a relay which drives dc motor..Is it efficient to use single transistor or do i require two transistors? I saw some designs which uses two transistors to drive single relay..

 

[kam1787]

Hi,
Some of these buttons have to drive a relay which drives dc motor..Is it efficient to use single transistor or do i require two transistors? I saw some designs which uses two transistors to drive single relay..

All depends. I suspect the two transistor circuits needed to;

- invert the signal and yet drive higher current, or
- higher current gain, or
- needed voltage and current gain.

Do you know the current required to latch your relay? Sounds like you need to invert the signal.

 

[SR19]

All depends. I suspect the two transistor circuits needed to;

Do you know the current required to latch your relay?

Dont know...is it possible to drive with ULN2003 as it sinks current?? if so ...how to connect it with relay?

 

[kam1787]

yes although kinda have to know what relay you are using; latching voltage and current

do you know if its a 12V relay? can you include a photo of it? can you connect it to 6V, and if that fails then try 12V? if either works, can you then measure the current?

Guess you will need at least voltage gain: **broken link removed** and **broken link removed** give the main idea. But common-emitter inverts the signal [Ov in gives Vout], so you will need two in series

 

[SR19]

yes although kinda have to know what relay you are using; latching voltage and current

do you know if its a 12V relay? can you include a photo of it? can you connect it to 6V, and if that fails then try 12V? if either works, can you then measure the current?

Guess you will need at least voltage gain: **broken link removed** and **broken link removed** give the main idea. But common-emitter inverts the signal [Ov in gives Vout], so you will need two in series

Hi,

Thanks for reply..Here is the relay datasheet..whenever a button is pressed, the 12v dc motor has to move forward, reverse..
how do i connect it with NPN transistor array or Darlington array..

 

[kam1787]

Hi,

whenever a button is pressed, the 12v dc motor has to move forward, reverse..

forward, reverse? what do you mean?

There are 3 models shown on the pdf file - would you be getting the 12V model?

 

[SR19]

forward, reverse? what do you mean?

Motor direction..control by seperate buttons..

 

[kam1787]

So the operation is OFF-FORWARD-REVERSE?

I think everyone assumed by your OP it was ON-OFF.

It is better to clearly and fully state what you are needing in the first post.


There are 3 relay models shown on the pdf file - would you be getting the 12V model?

 

[SR19]

So the operation is OFF-FORWARD-REVERSE?

I think everyone assumed by your OP it was ON-OFF.

It is better to clearly and fully state what you are needing in the first post.


There are 3 relay models shown on the pdf file - would you be getting the 12V model?

Yes...12vdc relay..