University Project..Need some help

Ganglia

Joined Mar 26, 2008
2
of course... putting a transistor in the motor circut, activated by the switch will make this alot more stable and would quite be my preferred way.

but the man wants something that is extremely low budget and by the looks of his posts, as simple as possible.

the motor would not be a very powerfull one either.

and about the magnets interferring with the motor...
if the motor is situated in the rear of the fan housing and the magnets/switch in the front the problem would not arise... remember we have the benefit of designing the entire system.

i know i'm pissing in a new pool here... but i have tried this with some jurryrigged components and it works alright.
 

rwmoekoe

Joined Mar 1, 2007
172
i'm into what sarge has told about the tiny vinyl blade fan. it is perfect, unless martgreg demands a 'real' common medium sized ac powered fan.

mrmeval has outlined the perfect way to go with this kind of fan (low voltage dc powered):
mrmeval said:
Use a current sense circuit to detect when the motor is blocked and have it shut off the motor.
Use a voltage sense circuit to detect when the unenergized motor is being spun
 

Søren

Joined Sep 2, 2006
472
Hi,

You allready got the best solution presented:
Use a current sense circuit to detect when the motor is blocked and have it shut off the motor.

Use a voltage sense circuit to detect when the unenergized motor is being spun.
The reverse, starting the motor before stopping it might be a tad easier though ;)

Would be dead-easy with a DC motor and slightly more complicated with an AC motor.

Are you up for soldering a small circuit together?
 

Søren

Joined Sep 2, 2006
472
Come to think of it - a childhood friend had a model aeroplane (a WWII Spitfire) in which the propeller was started and stopped manually in the same way - it just had a tiny motor and a batterycell IIRC, but it could hold its power for a long time, so I don't know if the motor had any special contacts, couplings or something (hey, I was 7 or 8 years old and wasn't allowed to dismantle my friends stuff).

Anybody else seen such like?
 

Thread Starter

martgreg

Joined Mar 24, 2008
17
Firstly I greatly appreciate all the tips effort and time from all you guys...

I dont mind soldering a few circuits as long as they aren't huge.. and also if i can find the components.. i am not adverse to learning but get flustered and think i need a quick fix...

So the two sensor circuits sonds liek he way to go...

I don't mind spending money how much i would like to keep motor and circuits within 100 - 200 bucks is this reasonable ....?? or do i need to shell out more... i can i have a rebate check coming :) but I also have a baby on the way too....

I dont mind it being super complicated if i could find someone who new what they were doing to do it or assist me in doing it...

I like simple bcoz i can follow a few basic instructions and do it :)

Thinking ahead I would prefer a AC motor as the use of the product is being evaluated an plugging it in the wall is one of the steps involved so i would rather just have a regular plug and not a little transformerbox... however if push comes to shove then i guess DC will suffice...

I think my first job is to spec out a motor and go from there... so i will do this by the weekend I hope even then i am still a little uneducated so i need to research...

Here are some rough schematic images . The total length of each blade is 10 - 13 inches and in the config shown they span about 22 inches tip to tip.

The hight off the ground at the moment is as appears may be 30 inches....

so these blades aren't small .. they are large with a 13 degree pitch so motor i guess needs a goot bit or torque.. and most likely will spin at somewhere between 150 - 300 ( have to test this too lol.. )

once i faricate som etest blades i can see what is a good speed..... i hope


also i have found the product which gave me some of these ideas.... which is pretty similar to what i want...

http://www.next.de/download/ventilux/VENTILUX_facts.pdf

motor info and speeds is shown in specs...


still need to work this out...will keep you posted....


thanks again for all your help guys



 

Thread Starter

martgreg

Joined Mar 24, 2008
17
I have almost decided it is ok to go with DC.

Here are some questions you guys might help me with..


1. Because if I can use a brushless one it will be quieter than a brushed right , yes/ no

2 Earlier in this thread Soren said that DC would be a lot easier than AC in my original requirements. This is for going the voltage sensor and current sensor circuits.

So now i have two options

a.Use the above mentioned approach using sense circuits....

b. Use a mechanical method.. un proven but looks possible.. below


I think I have come up with a mechanical solution to what I want to attempt using a

"momentary" Micro switch normally open (off)
an slip clutch with a actuator arm ( piece of plastic) glued to it.
dc brushless motor

http://www.anaheimautomation.com/brushless_dc_spur_gear_motor.aspx
BLWSG235D-36V-4000-R12.5


Driver

http://www.anaheimautomation.com/brushlessdcdrivers.aspx


Basically the clutch is on the motor axle.. so when it is span around, it has enough force to depress the switch but then slips when it reaches enough force from the support the switch is resting on... therefore it constantly slips and depresses the switch to the on position.

when the fan is grabbed and turned back for example a 1/4 of turn the actuator on the clutch is moved of of the switch and the motor is off.

Here is a basic set up ....

http://img245.imageshack.us/img245/8962/test.jpg









will i have problems using a micro switch in a dc system/and driver...

will there be an issue of it being a momentary switch that is always on?

burn out , or not be strong enough?

I really need some directions and would appreciate some advice...

kindest regards

mart greg
 

Thread Starter

martgreg

Joined Mar 24, 2008
17
"Momentary" means only that the switch returns to idle state when not being actuated.

I also ran across the following: http://www.goldmine-elec-products.com/prodinfo.asp?number=G16165

If it were me, I'd run with Soren's suggestion. Mechanics can be a such pain to adjust.

Thanks Thingmaker:



so it has to be clicked on and then clicked off ..... it wont turn off when the pressure is released ?


so is there a micro switch or small switch that acts like that of what a door bell does. there must be
 

Pich

Joined Mar 11, 2008
119
If you are using a motor driver the micro switch will only need to supply control current.
In most drive they can be set up so that closing a contact will run the motor and opening will stop the motor. You will need to look for the control operation on the DC driver before you buy it. Be careful on the motor you use, a very high gearbox ratio (to get low speed) will have high torque at the output shaft making it hard to stop and turn by hand.
 

Thread Starter

martgreg

Joined Mar 24, 2008
17
No. It turns on when we apply pressure and off when we release. (Or vice versa, depending on switch.) The click-click kind are not "momentary."

right that is what I want.... a switch that in on when pushed and of when you finger actuator is released....


where can i find this kind of switch ?

does it have a name that can help me search ....

i am going crazy... lol trying to find a solution....

http://www.superdroidrobots.com/shop/item.asp?itemid=507 ... this says it is a momentray micro switch..
 

Thread Starter

martgreg

Joined Mar 24, 2008
17
If you are using a motor driver the micro switch will only need to supply control current.
In most drive they can be set up so that closing a contact will run the motor and opening will stop the motor. You will need to look for the control operation on the DC driver before you buy it. Be careful on the motor you use, a very high gearbox ratio (to get low speed) will have high torque at the output shaft making it hard to stop and turn by hand.

thanks pich... i didnt even consider the strength of a geraed motor ...

:) more stuff to think about
 

rwmoekoe

Joined Mar 1, 2007
172
hey,
what thingmaker had come up with is perfect!
the one he presented here: http://www.goldmine-elec-products.com/prodinfo.asp?number=G16165

you only need to adjust its radius from the center of rotation to set the sensitivity, and add a weight ballast at the opposite from the pole to balance the system.

you can use any kind of motor with this one.
but you still need to use a transistor or micro relay, that switch on/off a bigger relay, that switch on/off the fan.
 
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