implement relay matrix using uln2003

AnalogKid

Joined Aug 1, 2013
10,987
how to implement relay matrix using uln2003 without using any gate?
That cannot be done. The ULN2003 is a low side driver *only*. To form a switching matrix you need both low and high side drivers.

Your question is very poor and has almost no details needed to discuss a solution.
What is the matrix switching?
What is controlling the matrix?
What is the matrix?

ak
 

Thread Starter

kooldude

Joined Feb 15, 2018
18
basically there will be one gpio expander 8+8 is there with that we will make 8*8 relay matrix....and only one relay need to be selected..
 

dendad

Joined Feb 20, 2016
4,452
Do you have any information that can help us help you?
Controller?
What sort of relay? --- Relay coil voltage and current.
Why a matrix and not just a number of port expanders? --- That would allow any relays to be operated, not just one at a time.
 

AnalogKid

Joined Aug 1, 2013
10,987
Besides the ULN2003 low side drivers, you need some kind of high side driver.

Is this homework or a school project?
Why are you not allowed to use gates?
Why must you use only ULN2003's?
Why do you have two threads on the same topic?

ak
 

dendad

Joined Feb 20, 2016
4,452
LED_Matrix.jpg
S1 on (high side) and S4 on, (low side) lights D1.
Other switch combinations for the other LEDs.
Generally, only one LED at a time in this particular example.
The number of high side and low side switches can be increased to end up with n(highside) x n(lowside) combinations.
If you just had high side switches in the above example, only 3 LEDs could be independently driven.
Adding the extra 3 low side switches allows 9 LEDs.

If you really want to get a bit confused, Google "Charlieplexing" ;)
 

AnalogKid

Joined Aug 1, 2013
10,987
Why do we need one high side driver and low side driver in the relay matrix?
It is a consequence of a design tradeoff. If you have 48 relays you want to control, one way to do that is tie one end of all of the relays to V+, and have 48 driver transistors (in 7 ULN2003's) , one for each relay. You can turn on any of the relays in any combinations but that's a lot of parts.

If you arrange the relays in a 6 x 8 matrix, two things change. One is that you now can turn on only one relay at a time. The other is that you need only 14 drivers, one for each row and column. BUT, the tradeoff is that the row drivers and column drivers must be different, because on is sourcing current *into* the relay coil and one is sinking current *out of* the relay coil. From the point of view of a transistor, those are two different current directions, and the "semi" in semiconductor means current can flow only one direction in a device.

ak
 
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