Check My Schematic?

[StAnkys]

I am using a variable resistor (like a pot, but not quite) to send a signal to a separate controller.  I want to step down a 24V battery pack to 12V (voltage regulator) to power a fan, then to 5V (voltage regulator) to run through the variable resistor voltage divider.

Is my schematic correct?  Will it output the 0-4 volt signal I am expecting?  or do I have to ground the regulators/fan/etc some other way than running them straight into the negative battery terminal?  or am I completely missing/overlooking something?




Thanks!

[SmAsH]

no, that schematic looks ok...
all gnds should be connected so that's good.
you do realize that this will waste a heap of power, yes?

[StAnkys]

The voltage regulators are NTE966 and NTE960, respectively.  They output 1A.

The fan is a small 12V computer fan, which draws 0.11A.

The Vout is the signal going to a separate controller.

[StAnkys]

no, that schematic looks ok...
all gnds should be connected so that's good.
you do realize that this will waste a heap of power, yes?

Considering I'm running a large 24 Volt motor with the same battery pack (8Ah pack), I'm hoping it won't affect battery life too drastically.  I want to move to switching regulators eventually, but the electronics store didn't have any.

Do you have any recommendations for a better setup?

[SmAsH]

well, i may suggest using a separate 12v pack to the motor driver because the motor may introduce some "noise" to the circuit and this can screw up some of your sensor readings.
is the 12v running a fan?

[Soeren]

Hi,

Is my schematic correct?  Will it output the 0-4 volt signal I am expecting?

No, you need to swap R1 and R2 since the potentiometer does NOT go from infinite to 50 kOhm, but from ~0 Ohm to 50 kOhm

But it is a very strange and inefficient circuit, what are you using the 0V-4V to (and what current do you need)?
There's better ways, especially if you need the variable voltage to be stable.

Apart from all that, you need to add several capacitors of different value, or you have just produced a very weird oscillator.

Tell us your exact needs and "haves" and a better solution will appear.

[StAnkys]

well, i may suggest using a separate 12v pack to the motor driver because the motor may introduce some "noise" to the circuit and this can screw up some of your sensor readings.
is the 12v running a fan?

The motor is 24V 350Watt.  I previously had a separate 9V running the circuit (without fan), and this is an attempt at running the whole processes off the same main battery pack.

Yes, the only purpose of the 12V is running the fan (and avoiding overheating from going straight 24V-->5V).

[StAnkys]

Hi,

Is my schematic correct?  Will it output the 0-4 volt signal I am expecting?

No, you need to swap R1 and R2 since the potentiometer does NOT go from infinite to 50 kOhm, but from ~0 Ohm to 50 kOhm

But it is a very strange and inefficient circuit, what are you using the 0V-4V to (and what current do you need)?
There's better ways, especially if you need the variable voltage to be stable.

Apart from all that, you need to add several capacitors of different value, or you have just produced a very weird oscillator.

Tell us your exact needs and "haves" and a better solution will appear.

This particular variable resistor goes from infinite Ohm down to ~50kOhm.  It's like a reverse-pot.  Here is a link:
http://www.trossenrobotics.com/flexiforce-25lb-resistive-force-sensor.aspx
So I want the Vout to be 0V when not engaged, and vary up to about 4V when fully engaged.

The variable voltage does not have to be "stable" per se, because it is being used as control signal (as in, active input where zero does nothing and 4V gives max power to the motor via a speed controller).  Because it is simply a sensing signal, the max current is ~5mA through Vout.


I've successfully run a similar circuit, but with the use of an Arduino microcontroller in the form of:
9V battery --> Arduino --> voltage divider part of circuit (via 5V regulated output of microcontroller) --> analog input sensing 0-1V (different resistor values, but this input number is irrelevant anyway) --> program to convert input value to a 0-4V output value --> output analog value

I'm trying to eliminate the microcontroller entirely, and also get rid of the need for a separate battery for just the sensing circuit (in this case, the 9V).


Hope this helps 

[nixter]

Hi!... I have a similar situation (not as complex) where i needed help with how to wire something up. I want to wire 2 computer fans to individual potentiometers with each having on/off indicator light.  I am not sure how all the different ratings and all fit in together, if i need resisters, or anything else. Also tried straight wiring one of the fans through the pot and the fan would only spin when pot was in 85-100% range. Is my power source too weak? The LED's, how do i wire them if i will be having variable voltage controlling fans, or do i not? Confused :/


I have:

* power source: 12v 1.25A adapter (but if needed to, can find another one).

*2 pots: mini volume control pots from radioshack, 10k with audio taper, SPDT switch, rated for 3amps 30V, rated power
  .05 watts, sliding noise <47mV).

*2 leds (w/ built-in 1/4W, 680-ohm resister for 12VDC operation; max ratings: power dissipation 180mW, forward voltage
           12V, forward current 15mA)

*fan #1: labeled 12V and .12A

*fan #2: labeled as 12V and 1.14W

Any help at all would be greatly appreciated. Thanks!!!!!!!!!!!!!!!

[corrado33]

Nixter try not to cross post.  We've already given you suggestions in your thread http://www.societyofrobots.com/robotforum/index.php?topic=10942.0.  Posting in multiple places doesn't necessarily mean you'll get faster results.  It just makes for a messier forum.