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Topic: What kind of motor driver to use for my Chem E car project (Read 1 time) previous topic - next topic

wvmarle

It never crossed my mind to ask the manufacturer, I will try that now.
Or the shop that sold you the stuff, of course.

In your case you may be better off ordering stuff off the Internet, then at least you can order things you have technical documentation of (make sure you have that before you press the Buy Now button).

Quote
Thanks The motors have 2 wires. Do I need all 4 motors to run the car?
I'd say so. The wheels won't run smoothly by themselves, with those motors attached.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

Daz1712

I think you have put the cart before the horse.

E.g. my friends said they would give me a horse,  so i ran out and bought a cart to be towed by a horse, then my friends turned up with a minature pony that fitted IN the cart.

Not knowing the voltage and current you will be able to provide means you are making some bad decisions based on assumptions with no basis in reality.

Break the project down.

First assemble the power sourse and do some tests to find out what you have.
1. How much does it weigh?
2. How big is it.
3. What Volts can it supply at What Amps?
4. How long will your supply last and how long do you need it to last.

 You mentioned using thermoelectric generators and making up two aluminum containers to hold your hot and cold water.
Do you realise that the aluminum will radiate heat on all 5 sides not just the side you attach the generators to?
Maby you could use two insulated containers with one wall replaces by aluminum sheet and sealed around the edge with silicone, giving you a surface for the generators.

Do some tests on your carrage to see how much current (Amps) it takes to drive it?

This is the start, you will have facts to let people know so they can help you

slipstick

I.e. go back to the questions I asked you way back in post #1 and find a few more answers. Without them you have no idea if anything will work. E.g. if your generator can't produce enough power to run even one motor it doesn't matter whether the chassis needs all four motors or not you still won't be going anywhere.

Steve

Mond3

Or the shop that sold you the stuff, of course.

In your case you may be better off ordering stuff off the Internet, then at least you can order things you have technical documentation of (make sure you have that before you press the Buy Now button).

I'd say so. The wheels won't run smoothly by themselves, with those motors attached.
Still awaiting reply from the manufacturer. The shop guys asked me to check online.

I think you have put the cart before the horse.

E.g. my friends said they would give me a horse,  so i ran out and bought a cart to be towed by a horse, then my friends turned up with a minature pony that fitted IN the cart.

Not knowing the voltage and current you will be able to provide means you are making some bad decisions based on assumptions with no basis in reality.

Break the project down.

First assemble the power sourse and do some tests to find out what you have.
1. How much does it weigh?
2. How big is it.
3. What Volts can it supply at What Amps?
4. How long will your supply last and how long do you need it to last.

 You mentioned using thermoelectric generators and making up two aluminum containers to hold your hot and cold water.
Do you realise that the aluminum will radiate heat on all 5 sides not just the side you attach the generators to?
Maby you could use two insulated containers with one wall replaces by aluminum sheet and sealed around the edge with silicone, giving you a surface for the generators.

Do some tests on your carrage to see how much current (Amps) it takes to drive it?

This is the start, you will have facts to let people know so they can help you
I should have the above information by Monday hopefully. Regarding the heat radiation, I was considering providing thermal insulation around the containers. to prevent heat dissipating outside the containers.

I.e. go back to the questions I asked you way back in post #1 and find a few more answers. Without them you have no idea if anything will work. E.g. if your generator can't produce enough power to run even one motor it doesn't matter whether the chassis needs all four motors or not you still won't be going anywhere.

Steve
Will do. I really appreciate everyone's help. Honestly I was lost as to where to start and you guys really help me get into the right direction.

allanhurst

I think your next job is to build and measure the thermoelectric generator.


Satellite ones use Pu239 at about 1000K as the source, and radiate waste heat into space at a very low temperature.

I don't think you'll get much from hot and cold water.

Allan

Mond3

I think your next job is to build and measure the thermoelectric generator.


Satellite ones use Pu240 at about 1000K as the source, and radiate waste heat into space at a very low temperature.

I don't think you'll get much from hot and cold water.

Allan
Build and measure Is my next plan indeed. I'm using boiling  water and a mixture of ethanol and dry ice.

ardly

Quote
Honestly, I have heard of Raspberry Pi but not of Audrino. It is listed in the thesis they want me build, that is the first time I heard of Audrino.
The Arduino is better suited to this than task than the Pi and simpler to setup. However since all you are doing is starting the car, running it in a straight line and then stopping (no steering or any significant control) I am not sure that a wholly electrical solution might not be better - but I don't know much about electronics.

You might find the motors generate a different amount of power when given the same voltage. So a bit of experimenting to pair the motors up might help so that both motors at the rear are similar and both motors at the front are similar. You could also experiment with just two motors and having front or rear drive. Presumably you will just lock the steering so that you go in a straight line.

I was surprised to read recently that the UAE are major importers of sand. Does Bahrain import a lot of sand as well :)
 
"Facts do not cease to exist because they are ignored" - Aldous Huxley

Daz1712

Hi again,

Was just checking back ansd thought i would add some thoughts.

To everyone.  This project seems to be about chemical engineering so it is required to use chemical methods to generate a drive for the car eg thermal to electric  (Although as a laugh i would love to present a peterol driven car claiming it has both a chemical and thermal element while powering the wheels)
The second part is a chemical timer designed to stop the car after a period of time.
Much as we think the arduino can do it that is not the purpose here.

The paper that you linked to had a lot to say but left out a lot of details.

How did they end up configuring the thermo generators? What model generator did they use? What voltage/current did they end up getting?
Starting to repeat my self here.

Any how you have a few areas to cover.
This is just a broad look at the planing ahead that i hope will allow you to come up with more questions.

The Generator:
You will need some electrical know how and a multimeter as what you have is several (think they mentioned 8) generators that will output a certain voltage at a certain current and you will have to wire some in series to obtain 6 volts (going by the photo of your 4 wheeled chassis i see a battery holder for 4, 1.5 volt AA batteries that appear to be in series giving you 6 volts)
and you will then have to wire others in parallel to increase the current to a level to drive the motors.
Notice how they used "SEVERAL BATTERIES" to simulate the thermo electric supply for testing.

The Timer:
The LED and the LDR are just used as a light detection circuit, ( lot like the street lights but in reverse ) when the light level is high eg the liquid is clear, the car engine is turned on and when the light level drops below a predetermined level the motor is turned off.
This happens as the liquid in the tube goes from clear to foggy.  I dont think the colour matters.
The main purpose is for you to figgure out the balance of chemicals to change the liquid from clear to opaque in a preset time .
The arduino will give you a number between 1 and 255 as the liquid inhibits the path of the led light through it.
You can find many examples of code for this.

The Drive Chassis:
You are going to need that multimeter (dont spend heaps or borrow one,  needs to measure up to say 50 volts DC and 10 amps DC).
Google 'using a multimeter to measure current and voltage' Go Youtube!
Set up the battery pack and connect it to one of the motors with the meter set to measure current, this will give you a starting current for one motor.  Note that the current may/will go up when you actualy add strain/load to the motor.
When you connect a wheel to the motor can you turn the wheel with ease? (called freewheeling) if not then you will need to run all 4 motors to make the buggy move or you will have the unpowered wheels acting as breaks.
Depending on the current available from your thermo supply you may run two motors and just run a shaft on the other two wheels.
There are many motor driver boards available for the arduino or just a simple relay board.  No need to get complicated with transistors or fetts as you will have enough to do as it is.  Try to stick to off the shelf, ready to go stuff.
You might want to check on the speed of that chassis loaded with some weight.

The Arduino:
Here i fall down as my programming is all theory but there are more here than just me
Note they dont say it but the graphic of there cart shows a 9 volt battery that i suspect they are using to run the Arduino as i think your thermal battery will be to unstable running the motors and the Arduino.
The project is to drive the car and use a chemical timer, nothing said about running the Arduino.

More to think on!

Mond3

The Arduino is better suited to this than task than the Pi and simpler to setup. However since all you are doing is starting the car, running it in a straight line and then stopping (no steering or any significant control) I am not sure that a wholly electrical solution might not be better - but I don't know much about electronics.

You might find the motors generate a different amount of power when given the same voltage. So a bit of experimenting to pair the motors up might help so that both motors at the rear are similar and both motors at the front are similar. You could also experiment with just two motors and having front or rear drive. Presumably you will just lock the steering so that you go in a straight line.

I was surprised to read recently that the UAE are major importers of sand. Does Bahrain import a lot of sand as well :)
 
I will get to the motors as soon as i figure out the wiring.

Bahrain used to export sand until they started to run short.
Tiny is;and really. I don't know what they were thinking.
Hi again,

Was just checking back ansd thought i would add some thoughts.

To everyone.  This project seems to be about chemical engineering so it is required to use chemical methods to generate a drive for the car eg thermal to electric  (Although as a laugh i would love to present a peterol driven car claiming it has both a chemical and thermal element while powering the wheels)
The second part is a chemical timer designed to stop the car after a period of time.
Much as we think the arduino can do it that is not the purpose here.

The paper that you linked to had a lot to say but left out a lot of details.

How did they end up configuring the thermo generators? What model generator did they use? What voltage/current did they end up getting?
Starting to repeat my self here.

Any how you have a few areas to cover.
This is just a broad look at the planing ahead that i hope will allow you to come up with more questions.

The Generator:
You will need some electrical know how and a multimeter as what you have is several (think they mentioned 8) generators that will output a certain voltage at a certain current and you will have to wire some in series to obtain 6 volts (going by the photo of your 4 wheeled chassis i see a battery holder for 4, 1.5 volt AA batteries that appear to be in series giving you 6 volts)
and you will then have to wire others in parallel to increase the current to a level to drive the motors.
Notice how they used "SEVERAL BATTERIES" to simulate the thermo electric supply for testing.

The Timer:
The LED and the LDR are just used as a light detection circuit, ( lot like the street lights but in reverse ) when the light level is high eg the liquid is clear, the car engine is turned on and when the light level drops below a predetermined level the motor is turned off.
This happens as the liquid in the tube goes from clear to foggy.  I dont think the colour matters.
The main purpose is for you to figgure out the balance of chemicals to change the liquid from clear to opaque in a preset time .
The arduino will give you a number between 1 and 255 as the liquid inhibits the path of the led light through it.
You can find many examples of code for this.

The Drive Chassis:
You are going to need that multimeter (dont spend heaps or borrow one,  needs to measure up to say 50 volts DC and 10 amps DC).
Google 'using a multimeter to measure current and voltage' Go Youtube!
Set up the battery pack and connect it to one of the motors with the meter set to measure current, this will give you a starting current for one motor.  Note that the current may/will go up when you actualy add strain/load to the motor.
When you connect a wheel to the motor can you turn the wheel with ease? (called freewheeling) if not then you will need to run all 4 motors to make the buggy move or you will have the unpowered wheels acting as breaks.
Depending on the current available from your thermo supply you may run two motors and just run a shaft on the other two wheels.
There are many motor driver boards available for the arduino or just a simple relay board.  No need to get complicated with transistors or fetts as you will have enough to do as it is.  Try to stick to off the shelf, ready to go stuff.
You might want to check on the speed of that chassis loaded with some weight.

The Arduino:
Here i fall down as my programming is all theory but there are more here than just me
Note they dont say it but the graphic of there cart shows a 9 volt battery that i suspect they are using to run the Arduino as i think your thermal battery will be to unstable running the motors and the Arduino.
The project is to drive the car and use a chemical timer, nothing said about running the Arduino.

More to think on!
Yes, you are on point about the project and there are definitely alot of information missing from the paper which i am left to ponder with.
Thank you so much for taking the effort to list out the areas. Now at least I know where to focus on.
I will try to use batteries to simulate the generators. Although I can only use that for tests.
Regarding the LDR; The iodine clock reaction turns the mixture from clear liquid to blueish black mixture. It pretty dark, Think the LDR could pick up the change?
The multimeter is available witht he university, so I'm glad I don't have to buy that.
No, there is no freewheeling feature for the buggy.
Just to know if I understood right, using all 4 motors would require more current over using 2 motors. Could the load/weight increase require more power on 2 motors over 4 motors?
When you say run a shaft between two wheels, you mean pass a pipe between the wheels yeah?
The shop guy advised me to consider L293D sheild board saying it is purchased often. What do you think.
You have a point about using the audrino with battery. Thank you again!
Once again I really appreciate all the efforts you and the community here has been putting to help me out. You guys are really awesome.

ardly


Quote
Just to know if I understood right, using all 4 motors would require more current over using 2 motors. Could the load/weight increase require more power on 2 motors over 4 motors?
Using 2 motors will use less current. However if the buggy is too heavy you might need 4 motors to move it. Since there does not seem to be any speed requirement if you run the buggy on a flat smooth surface you may well get away with 2 motors, try it and see. You could put 4 AA batteries in the buggy and put weights onto to it see what is practical.

If the motors cannot freewheel, and you want to use only two, then you will need to attach a couple of wheels without motors.


Quote
Regarding the LDR; The iodine clock reaction turns the mixture from clear liquid to blueish black mixture. It pretty dark, Think the LDR could pick up the change?
Yes.

Quote
Bahrain used to export sand until they started to run short.
Tiny is;and really. I don't know what they were thinking.
Yes, it seems the world is running out of sand. That is why your neighbours in the UEA are such big importers. In the Philippines several islands have disappeared completely because of 'sand pirates' stealing the stuff.
"Facts do not cease to exist because they are ignored" - Aldous Huxley

Daz1712

I will get to the motors as soon as i figure out the wiring.

Regarding the LDR; The iodine clock reaction turns the mixture from clear liquid to blueish black mixture. It pretty dark, Think the LDR could pick up the change?
The multimeter is available witht he university, so I'm glad I don't have to buy that.
No, there is no freewheeling feature for the buggy.
Just to know if I understood right, using all 4 motors would require more current over using 2 motors. Could the load/weight increase require more power on 2 motors over 4 motors?
When you say run a shaft between two wheels, you mean pass a pipe between the wheels yeah?
The shop guy advised me to consider L293D sheild board saying it is purchased often. What do you think.
You have a point about using the audrino with battery. Thank you again!
Once again I really appreciate all the efforts you and the community here has been putting to help me out. You guys are really awesome.

Hi again, thanks for listening to the replies.

With the LDR you will have to wire it to one of the ADC Pins (look for the tutorials, they will show you wireing and code examples) when wired the LDR (Light Dependent Resistor) will reduce in resistance the more light it detects and this when wired up will give you a voltage that the Arduino can detect and convert to a number between 1 and 255. 
You will have to set up your LED and LDR through your liquid mix and do some tests to see your max/min readings and using if/then you can turn the motors on and off.
Remember the LDR detects any light so you will need to either shield it from or allow for other light sources, like the room light.

In ref to the motors, yes running 4 motors will take four times the power but depending on the total weight you may need all 4 motors to get your car moving.

If you try to tackle this project from all angles you are going to get into trouble unless you are a wiz at project management.

-So start with the power pack. Until you know what voltage and current you have for what weight you will be guessing on the rest.

-Then to the timer as this will also go towards the weight.

-Once you have these two (the major weight items) you can then work on the chassis.

You can test one motor and know what the minimum current to run all 4 motors will be and then load it up with the equivelent weight and see how much current it takes to start it rolling.
Remember, the most/highest current is on takeoff coasting or cruising uses the least.

In ref to the motor shield you need to consider the following (Think of this while testing the chassis).

- do you need to go backwards and forwards.
- do you need to start slow, this will require motor PWM control or can you just apply power direct to the motors using a relay and starting with the screech of tyres, the smell of burning rubber and fishtailing across the floor.
OK i may have got a bit carried away on that last bit (or not).

Still the board recomended will give you options where as the relay is stop/go and does seem to be recomended by the shop you got the chassis from.

You still have a lot of unknowns that will need answers before you can get more answers that may be wrong (for your project) based on the little you know now.

I think it safe to get the parts mentioned although the motor controller mentioned does come up as obsolete when i google it, but there are replacements.
Then go to work on the power supply because you need to know the following.

-Whats the model of these thermal units? (havent seen it mentioned so dont know the specks)
-Whats the voltage output from one unit and how much current will it supply at what voltage? (Usualy in the specs)
-Test one motor for current drawn so you have a starting point on what you will require from the supply.

The other thing not mentioned is how far does the car need to travel?  Will the themal battery provide the needed power long enough?

Good Luck remenber you can tackle one thing at a time with ease after that you may begin to introduce errors and make more work for yourself.


allanhurst

Since you're doing a Chem E project, why not build a chemical battery - eg an old-fashioned bichromate cell?  ( look it up).

That might amuse your supervisors   ......

Allan

Mond3

Hello people,
I have been quite busy hence was not able to update the progress over here. I Have managed to assmble the car. With six thermo electric generator i get a max volt of 19V. The first test i conducted I was able to run the car. Further tests seems to be a failure. With the exhibition being after 2 weeks that kind of sucks. Currently I think the problem is that the thermoelectric generators do not produce enough amps. Last I checked they produce about .2 amps which is probably why it dosen't run . But that still leaves me confused as to why the car was running in the first trail. Any tips to increase the amps current produced? I am able to run the car just fine when powered with a power bank of 2100 mA. The car setup with the hot and cold sink filled weight around 1708g. I have simulated this weight with the power bank and the car seems to run just fine.
I have all aspects of the project working except for this aspect which is honestly quite frustrating. I dont need to run the car for long. Even 20-30 seconds is fine really. I have conducted a few tests so hopefully i should have answers to some of the questions this tine around. Appreciate any headers on this. Thanks again.

allanhurst

Hotter and colder water  (ice , plus salt to take it down to -> 0F) ?

( See Mr Fahrenheit's work, which is where he got the 0F from)

Calcium chloride might be better.... three ions rather than two, one of them Ca++ ,  and much more soluble.
 Remember 'depression of freezing point'  lecture?

Good insulation around your tanks?

Thermal grease on the thermo cells to make good thermal contact?

Or ( bit late now) see my previous post. Or Daniell cells?

What voltage does your thermoelectric generator produce when loaded with 2 amps?

A buck convertor to take it's 19v down to your motor voltage might be useful. Much more efficient.And stable.

Allan

Mond3

I'm using Dry ice and ethanol mixture for the cold tank which is maints at -70C. The temperature gradually starts dropping but at a much slower rate than the hot sink. If you see the attachment I have provided in the previous post, i have insulated the tank with fibreglass tape around it which according to the manufacturer is excellent insulation. And yes I have used thermal past on both sides of the thermo electric generator. I did check about the project you suggested, I was not able to find much information on it and also I had already done my theory last semester on this car. Changing the project would require having to prepare the theory from scratch which is hectic. "What voltage does your thermoelectric generator produce when loaded with 2 amps?"
I am not sure I get what you are asking. I loaded the car chassis with the same wieght as the container and then used a power bank that supplies upto 2amps to power this car. I did this test to eliminate weight factor as a reason for the car not working. Not sure how to mount 2amps on the thermoelectric generators. I could use a buck converter but currently I think my main issue is lack sufficient amps so how do I go about this.

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