Starting DC motor based on squeeze pressure.

sailorjoe

Joined Jun 4, 2013
363
Regarding the R values? Probably showing my ignorance again but when you say use x for the r values where do I enter these values?
Oh, OK. Resistors R2 and R3 are variable resistors. They have an adjustment knob of some kind. You set their value by rotating the knob while you measure the voltage going into the comparator from the resistor. Google "trimmer potentiometer" to see examples.
 

Thread Starter

homer2121

Joined Jan 2, 2016
32
Ok to thanks this all very helpful. Just to make sure i have this straight these are all the components I need and their specs. Correct me if I am wrong on something.

1. Batteries totalling 6v
2.6v dc motor
3.Force sensitive resistor
4.LT319A dual comparator..(is this sufficient for the current a 6v motor would need?)
5.MOSFET that can hold at least 6v and is p-channel
6.three to four inch perf board
7.on/off switch
8.diode
9.four resistors?? We haven't talked about these much is there a certain kind I need?

Is this it?

Thanks
 

djsfantasi

Joined Apr 11, 2010
7,410
There is a model of Arduino, the Pro Mini, which is 0.7x1.3". This might fit into your broom handle. Programming isn't as convenient as other models with USB, but it's size may be right.

An Arduino compatible uC is the Adafruit Pro Trinket. Is is also 0.7" wide and has a USB interface for loading.
 

sailorjoe

Joined Jun 4, 2013
363
Well, so now we know that your motor needs only 2.6 volts to operate. It's probably OK to use 3 volts as well. How much current does it need? That's an important spec.

So we need to add something to compensate for the low voltage motor. I recommend a zener diode with a zener voltage of as close to three volts as you can find, and capable carrying the current the motor requires.

For the resistors, any 1/4 watt carbon or carbon film resistors will work, they just need to be the correct values, and even that isn't particularly critical. I chose relatively high values to minimize battery drain, but if you jut need to demonstrate something one time, it's not that important.

I didn't include it on the diagram, but you might find it helpful to add a capacitor, 1uF, connected from power to ground right at the comparator. This will help stabilize the operation of the comparator.
 

MaxHeadRoom

Joined Jul 18, 2013
22,390
The voltage for the motor is not at all critical when some kind of rpm controller is used, the problem with too high a voltage when uncontrolled is rpm, in this case the rpm can be limited to the motor maximum.
Max.
 

Thread Starter

homer2121

Joined Jan 2, 2016
32
Ok
Well, so now we know that your motor needs only 2.6 volts to operate. It's probably OK to use 3 volts as well. How much current does it need? That's an important spec.

So we need to add something to compensate for the low voltage motor. I recommend a zener diode with a zener voltage of as close to three volts as you can find, and capable carrying the current the motor requires.

For the resistors, any 1/4 watt carbon or carbon film resistors will work, they just need to be the correct values, and even that isn't particularly critical. I chose relatively high values to minimize battery drain, but if you jut need to demonstrate something one time, it's not that important.

I didn't include it on the diagram, but you might find it helpful to add a capacitor, 1uF, connected from power to ground right at the comparator. This will help stabilize the operation of the comparator.[/QUOTE

Ok, if when I get the motor and the 6v one ends up being too large to fit I will be using an even smaller motor so I guess I better not get too far ahead of myself until I know exactly which motor I will use...will I still be needing 6v for batteries regardless?
 

sailorjoe

Joined Jun 4, 2013
363
There is a model of Arduino, the Pro Mini, which is 0.7x1.3". This might fit into your broom handle. Programming isn't as convenient as other models with USB, but it's size may be right.

An Arduino compatible uC is the Adafruit Pro Trinket. Is is also 0.7" wide and has a USB interface for loading.
You're absolutely right, and I hadn't considered the use of those types of "alternate Arduino" boards. Still, in a case like this, I think it's important to have a circuit that can adapt to the sensor rather than the other way around. I'm worried that the OP will have more work to do trying to get the sensor to meet the requirements of the Arduino. Plus, think of all the things you have to learn just to get an Arduino to read a sensor, when you don't know anything about programming, using an IDE, code structures, interface wiring, communications, etc. I think it's a level of complexity that's unwarranted in this case.
 

Thread Starter

homer2121

Joined Jan 2, 2016
32
You're absolutely right, and I hadn't considered the use of those types of "alternate Arduino" boards. Still, in a case like this, I think it's important to have a circuit that can adapt to the sensor rather than the other way around. I'm worried that the OP will have more work to do trying to get the sensor to meet the requirements of the Arduino. Plus, think of all the things you have to learn just to get an Arduino to read a sensor, when you don't know anything about programming, using an IDE, code structures, interface wiring, communications, etc. I think it's a level of complexity that's unwarranted in this case.
Here is another thought...how do the pressure sensors work? If I am able to wrap it around the handle there will obviously be multiple contact points (hands, fingers, etc) So will the sensor pick up on all of these points and add them all together or will it just read it as one point, whichever spot is pressed the firmest?
 

djsfantasi

Joined Apr 11, 2010
7,410
I am not going to disagree with you. Especially since the OP seems disposed to a discrete solution.

But keeping an open mind, code structures? Tons of examples online... Interface wiring? No more complex than discrete... IDE? Makes coding easier... Communications? This problem is not about it... I see three wires to a uC and some code, that's it (excluding grounds).

But! I am disposed to think in that manner. Coding is something I do in my sleep. Interfacing sensors to a uC? Interfacing LEDs or relays or motors? Done tons. And I learned to use an Arduino in about 15 minutes. But that is me. It is an area that comes naturally to me. So understand if I see solutions in that light.

The best solution is one that the OP can understand and reach with a little stretch.
 

Thread Starter

homer2121

Joined Jan 2, 2016
32
That, my friend, is exactly what you have to figure out with experimentation.
Ok well thanks for all your help and your patience with a newbie..other than those extra parts you threw in there depending on the motor is my list complete?
That, my friend, is exactly what you have to figure out with experimentation.
Here is some more info on the motors I have coming. I ordered a few so I can tinker. 5 that range from 1.5v-6v, they are 50,000 rpm and it doesn't give me current rating.

One that is 3v 1100 rpm 0.2A

5 that range from 1.5v-4.5v 1500 rpm and current rating ranging from 0.012-0.043A.

Most of them are sufficiently small but I am not sure if they will be powerful enough for what I want. I shouldn't need anything too powerful. I will be choosing the one that is the smallest in size that will meet my needs.

Does any of this info shed any more light on it?
 

Thread Starter

homer2121

Joined Jan 2, 2016
32
I am not going to disagree with you. Especially since the OP seems disposed to a discrete solution.

But keeping an open mind, code structures? Tons of examples online... Interface wiring? No more complex than discrete... IDE? Makes coding easier... Communications? This problem is not about it... I see three wires to a uC and some code, that's it (excluding grounds).

But! I am disposed to think in that manner. Coding is something I do in my sleep. Interfacing sensors to a uC? Interfacing LEDs or relays or motors? Done tons. And I learned to use an Arduino in about 15 minutes. But that is me. It is an area that comes naturally to me. So understand if I see solutions in that light.

The best solution is one that the OP can understand and reach with a little stretch.
I will obviously understand more once I get into it but to be honest both methods are completely foreign to me. I am willing to learn bc no matter which option I choose I have learning to do. I am mostly looking for whatever is going to work the best and most reliably, cost effective, and will fit inside the confined space I have to work with. If either option will meet those requirements then I want the option I will be able to execute with my very limited knowledge and some guidance. Whichever that may be.

Thanks
 

BReeves

Joined Nov 24, 2012
410
Teensy 2.0 is 0.7 inches wide, Arduino compatible, free software with plenty of sample code, USB programmable and they have a Forum where you can learn and ask questions.
http://www.pjrc.com/teensy/

This is what I went with in the stuff I do because it seemed easier to get started than the other micro options.
 

sailorjoe

Joined Jun 4, 2013
363
I will obviously understand more once I get into it but to be honest both methods are completely foreign to me. I am willing to learn bc no matter which option I choose I have learning to do. I am mostly looking for whatever is going to work the best and most reliably, cost effective, and will fit inside the confined space I have to work with. If either option will meet those requirements then I want the option I will be able to execute with my very limited knowledge and some guidance. Whichever that may be.

Thanks
Ok well thanks for all your help and your patience with a newbie..other than those extra parts you threw in there depending on the motor is my list complete?

Here is some more info on the motors I have coming. I ordered a few so I can tinker. 5 that range from 1.5v-6v, they are 50,000 rpm and it doesn't give me current rating.

One that is 3v 1100 rpm 0.2A

5 that range from 1.5v-4.5v 1500 rpm and current rating ranging from 0.012-0.043A.

Most of them are sufficiently small but I am not sure if they will be powerful enough for what I want. I shouldn't need anything too powerful. I will be choosing the one that is the smallest in size that will meet my needs.

Does any of this info shed any more light on it?
Yes, it does. Every motor you describe has a current rating. 3v 1100 rpm 0.2A. That 0.2 Amps, or 200 milliamperes. That's your current rating. What does the motor have to rotate, a fan perhaps?
 

sailorjoe

Joined Jun 4, 2013
363
I am not going to disagree with you. Especially since the OP seems disposed to a discrete solution.

But keeping an open mind, code structures? Tons of examples online... Interface wiring? No more complex than discrete... IDE? Makes coding easier... Communications? This problem is not about it... I see three wires to a uC and some code, that's it (excluding grounds).

But! I am disposed to think in that manner. Coding is something I do in my sleep. Interfacing sensors to a uC? Interfacing LEDs or relays or motors? Done tons. And I learned to use an Arduino in about 15 minutes. But that is me. It is an area that comes naturally to me. So understand if I see solutions in that light.

The best solution is one that the OP can understand and reach with a little stretch.
Absolutely agree. Those of us who have lots of embedded software and hardware development work under our belts sometimes forget how much we had to learn to make it all work. You learned the Arduino in 15 minutes; so did I, but we already knew a lot before that. For our OP here, I feel that minimizing the number of variables he has to deal with will be better for this project. Frankly, I think getting the handle sensor right is plenty of work all by itself.
 

Thread Starter

homer2121

Joined Jan 2, 2016
32
The big problem I can see is how to make the whole length of the handle respond to squeeze pressure. Maybe use air, an outer membrane with air between it and the hard handle. Some form of sensor that will read the air pressure change when the handle is squeezed. Just throwing out an idea...
That might be a solution. I do not want the handle to compress but perhaps if it compresses very minimally that would be ok. Again though, I wonder if the fact that it is being squeezed in multiple places would create an issue here as well.
 

Thread Starter

homer2121

Joined Jan 2, 2016
32
Absolutely agree. Those of us who have lots of embedded software and hardware development work under our belts sometimes forget how much we had to learn to make it all work. You learned the Arduino in 15 minutes; so did I, but we already knew a lot before that. For our OP here, I feel that minimizing the number of variables he has to deal with will be better for this project. Frankly, I think getting the handle sensor right is plenty of work all by itself.
Is this the variable resistor you are talking about?
http://www.amazon.ca/gp/aw/d/B008DF...e+resistor&dpPl=1&dpID=315n4S2zI3L&ref=plSrch

And which of these dual comparators(if any) will work?

http://www.amazon.ca/gp/aw/s/ref=is_box_hi?k=Dual+comparator
 

ronv

Joined Nov 12, 2008
3,770
Is this the variable resistor you are talking about?
http://www.amazon.ca/gp/aw/d/B008DF...e+resistor&dpPl=1&dpID=315n4S2zI3L&ref=plSrch

And which of these dual comparators(if any) will work?

http://www.amazon.ca/gp/aw/s/ref=is_box_hi?k=Dual+comparator
Don't get ahead of yourself with parts.
The electronics will be okay, what you need to buy are some of the pressure sensors and the equipment to measure the results. Then the values can be calculated. Right now no one knows how the sensor will respond, so you will need to do that experiment first.
So buy a little volt ohm meter and the sensor. Wrap it around the handle and see what the resistance is with various pressures.
 

Thread Starter

homer2121

Joined Jan 2, 2016
32
Also, do I buy a bigger perf board and cut it down to a smaller size or do I need to find one the right size?

I found some that are 5x7 cm but that is too big so can
Don't get ahead of yourself with parts.
The electronics will be okay, what you need to buy are some of the pressure sensors and the equipment to measure the results. Then the values can be calculated. Right now no one knows how the sensor will respond, so you will need to do that experiment first.
So buy a little volt ohm meter and the sensor. Wrap it around the handle and see what the resistance is with various pressures.
Ok thanks..there are a ton of these which one is sufficient?

http://www.amazon.ca/gp/aw/s/ref=is_s_ss_i_0_9?ie=UTF8&k=volt+ohm+meter&sprefix=Volt+ohm+
 
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