use a slotted disc (strip down an old mouse - there are the slotted discs and phototransistors). Use the weight idea and just sense when the disc moves. To make is less sensitive, use code or block up some of the notches. I buy mice for less than a dollar wholesale so this is a much cheaper way of doing it. Also consider using the speed pulse sender (if fitted - most modern cars have them) on the car. The slightest movement of the wheels is enough to give a pulse from one of these. Just my 2 cents worth Dominic ----- Original Message ----- From: "Pang" To: Sent: Tuesday, August 06, 2002 10:07 PM Subject: Re: [EE]: What is the estimated torque ? > Hi, > > Thanks for suggestions and questions. It shows I have not been thinking > thoroughly on the method of implementation. First of all, the application I > will be building is going to be a tilt sensor. If you still recall, there's > a few thread on this subject not too long ago and someone actually suggested > using a potentiometer to measure the tilting by attaching a certain amount > of weight to the shaft. I think the name 'tilt sensor' is misleading. > Tilting here is not a 180 deg upside-down turn. It is meant to be installed > in an automotive to detect towing. As such, I think an angle sensor will be > a more appropriate name. > > Thanks for highlighting the different aspect of torque calculation. What I > intend to do is to attach a weighting to the shaft. The potentiometer is > fixed to a flat board. Whenever the board is raised at either side, the > weighting will move the shaft. The weight that is atttached to the shaft > must be concentrated to a certain direction only, something like a pendulum. > Or let say the weighting is in the form of an arrow. The shaft will be > attached to the beginning of the arrow while the arrow will always point to > the gravity, assuming the end of the arrow is heavier than the beginning. > > phew.... i hope you guys understand my kindergarden level of description... > > I have enquire things like rotary encoder, position sensor, optical sensor > and angle sensor. But most of them are either costly or that they cannot > withstand much load to the shaft. It seems that the life of the ball bearing > will be greatly reduced. I am quite limited in my mechanical knowledge, > otherwise there are lot's of method of doing it. > > > What will be turning the pot? The weighting attached to the shaft > > > Will it turn the pot directly, or is there a > > knob/attachment/lever/belt/pulley/etc on the pot? > > The weighting will turn the pot directly ( that's the easiest method i could > think of ) > > > How much force is going to be applied to the point at which they (the > > pot and the other object) meet? > > ? > > > Are you also going to be dealing with friction/slipping? > > > I was thinking that the weighting will be attached permanently to the shaft, > the weighting will not slip but the shaft will be turn according to gravity. > > I have been searching for quite some time for a cheap solution (USD5 for the > potentiometer) but it seems not possible. The only way is still using the > accelerometer. > > Thanks for the explanation of the fan, the torque and the different force > required. > > Best rgds, > Pang > > ----- Original Message ----- > From: "M. Adam Davis" > To: > Sent: Tuesday, August 06, 2002 10:59 PM > Subject: Re: What is the estimated torque ? > > > > Your questions don't add up. > > > > I can turn a high torque anything with my finger if the knob is big and > > light enough. In other words, the force you apply with your finger > > translates to torque through a lever. If you have a small diameter > > shaft on your low torque pot, then your finger may have to apply a great > > deal of force to turn it, if you attach a 1 foot stick to it then your > > finger will have to apply very little force to the end of the stick. > > > > The fan blade is the same way. You'll apply less force at the ends of > > the blades then you'll apply at or near the center. > > > > The trade off is distance moved. At the center you only need to move it > > a little to get a large degree of rotation, whereas at the outside you > > need to move it further. Force * Distance = Work, the work is the same > > whether you turn it a the center or the end, but the distance and force > > changes. > > > > If you knew the torque you needed (ie, .01 foot pound or some other > > absolute torque measurement) then we could help you more easily. > > > > Since, however, you seem to be asking for a relative measurement (fans > > have widely varying torques) then you need to give a little more > > information: > > > > What will be turning the pot? > > Will it turn the pot directly, or is there a > > knob/attachment/lever/belt/pulley/etc on the pot? > > How much force is going to be applied to the point at which they (the > > pot and the other object) meet? > > Are you also going to be dealing with friction/slipping? > > > > By the way, a normal desktop fan requires a lot more torque to turn than > > any small pot I've ever dealt with. Take the fan blades off the shaft > > for a better torqure comparison. Better yet, put the fan blades on the > pot. > > > > I hope this helps! > > > > -Adam > > > > Pang wrote: > > > > >Hi all, > > > > > >Just received a sample for a low torque potentiometer. As i checked it, I > > >found that it is not suitable for my application. The torque is not low > > >enough eventhough the potentiometer is classified as low torque. As such > I > > >would like to enquire, what is the estimated torque such that I can turn > the > > >shaft of a potentiometer using only one finger? Or maybe in another > way... > > >what is the torque for a normal desktop fan? Is such a potentiometer > (with > > >that level of torque) available? > > > > > >Thanks.. > > > > > >Best rgds, > > >Pang > > > > > >-- > > >http://www.piclist.com hint: The list server can filter out subtopics > > >(like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > > > > > > > > > > > > > > > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.