Hello all,
First off, what a great site! I've been a lurker here for a while and am finally stumped to where I need to ask a question of my own. Here goes.
I have built an automotive circuit in my drag car, and the 40A bosch relay I'm using, needs a switching supply of 12V @ 30mA.
I am going to use a 0-5v variable output sensor to determine when to close the relay. I need a 12V ignition supply wire that runs into a series of capacitors @ X-ohms to bring the reference voltage down to 5V. Then on that same wire I want to run an adjustable X-ohm potentiometer to scale the reference voltage to an operator set value ~0-5v. This will then go into an on-board LED voltage display for ease of operation.
Here's where I get lost.
The comparator I started with is an LM2903. It seems that I should have V+ be the operator-set reference voltage, and V- be the variable sensor voltage, so any time the the variable sensor voltage exceeds the operater-set voltage, it starts to output. The one issue is, I have to use a TIP120 transistor with this comparator, in order to complete the ground-side of my relay @ 12V DC, 30mA.
Question,
Is there a comparator out there, that can take a V+ at operator-set ~0-5V, a V- at actual variable sensor output 0-5V, AND a 12V supply in, so that when V+<V-, it pushes 12V out of the comparator instead? Is that what Vcc supply is for?
Or am I stuck using a transistor....
Thanks in advance, any help is much appreciated.
First off, what a great site! I've been a lurker here for a while and am finally stumped to where I need to ask a question of my own. Here goes.
I have built an automotive circuit in my drag car, and the 40A bosch relay I'm using, needs a switching supply of 12V @ 30mA.
I am going to use a 0-5v variable output sensor to determine when to close the relay. I need a 12V ignition supply wire that runs into a series of capacitors @ X-ohms to bring the reference voltage down to 5V. Then on that same wire I want to run an adjustable X-ohm potentiometer to scale the reference voltage to an operator set value ~0-5v. This will then go into an on-board LED voltage display for ease of operation.
Here's where I get lost.
The comparator I started with is an LM2903. It seems that I should have V+ be the operator-set reference voltage, and V- be the variable sensor voltage, so any time the the variable sensor voltage exceeds the operater-set voltage, it starts to output. The one issue is, I have to use a TIP120 transistor with this comparator, in order to complete the ground-side of my relay @ 12V DC, 30mA.
Question,
Is there a comparator out there, that can take a V+ at operator-set ~0-5V, a V- at actual variable sensor output 0-5V, AND a 12V supply in, so that when V+<V-, it pushes 12V out of the comparator instead? Is that what Vcc supply is for?
Or am I stuck using a transistor....
Thanks in advance, any help is much appreciated.