Hi, this is just another tachometer as you can also find many tutorials out there. There are different approaches on measuring rpm, what I use here is based on analogRead method as written in arduino playground learning page (http: //playground. Arduino. Cc/Learning/Tachometer) but with some modification on calculation method of rotational frequency. The code in arduino playground is very good and understandable but there are some spaces for improvement. Because it reads the number of change in state over specific time frame, it may lose accuracy when we try to make fast reading on slow revolution speed. 7.
How to Install a Tachometer 8 Steps with Pictures wikiHow
Motor Wheel Assy: This is not the main interest in this project, basically any arrangement that provides a wheel with adjustable speed will do. Here I used a styrofoam disk driven by a used walkman motor connected to an AC/DC adaptor through a potentiometer. Clamps, base, etc are just from the backyard. The only important thing is to make window on the wheel such that the IR LED phototransistor can see each other sometimes while the wheel is turning. 6. Put the IR LED and Receiver facing to each other in a position that make them can see each other occasionally through the window on the wheel. Better to make them not to far apart. Create the shield (saying shield is somewhat fancy, actually only a circuit of limiting resistors *lol*), see the diagram. 8. Hook up with your arduino: connect the IR receiver to analog pin A5, see the diagram. Notice that the IR LED BM6886 and IR Phototransistor BPT6886 look alike, with two legs and clear head so make sure you are not mixing them. Connect the longer leg of LED to positive side of circuit (right after 655 resistor), but the longer leg of phototransistor should be connected to negative side of circuit (goes to the GND). 9. Hook up your motor (to drive the wheel), here i use external power supply to make it simple. Play safe, or use a motor shield. The code is pretty much similar to the one here: in fact i wrote based on that code. Only instead of counting how many times the sensors are saying hi to each other every certain period, I count how long until they can see the other again after the last meeting. Also, I find that using micros(), that returns microcontroller time in microseconds, gives a significantly more accurate result than if i used millis() on the same place.
Below is the code modification for checking the good number for sensorthreshold variable: The program writes the rev per second and rev per minute to the Arduino IDE serial monitor. Of course this project is very rough and simple, but can be a part of further development. I will come again once I have something else. See you later. . Thanks pinodisco! I've tried a couple of other tachometer tutorials but this one has ben the best and easiest to use. And I took it a step further and untethered the sensor from my computer by using an LCD from another instructable. Quick update, experimenting with conversion from RPM to MPH for a bicycle speedometer. I used the formula found here. Http: //mathforum. Org/library/drmath/view/65867. Htmlsorry i havent been around for a while (it's a super long while actually, haha). Other than money, knowing that others find my simple writings useful makes me really happy: ) actually i am going to make a project that involves a sort of vehicle speed sensor also, just like yours i will use my 66x7 lcd, thanks for sharing your reference that would be useful for sure: )OK. Disregard my comments below. I had a good look at a blow-up of the photo and I see it is where you have inserted the two resistors into the circuit. Sorry gray if my instructable is not really clear.
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However, glad you saw it. How does the 'IR Shield' fit into the scheme of things. I don't see it in your schematic and I cannot find one in the RobotShop. Let your inbox help you discover our best projects, classes, and contests. Instructables will help you learn how to make anything! AC Compressor clutch replacements usually cost more than compressor replacements because of the cost of the clutches and the cost of the labor added together. In most cases you end up getting a compressor that is about the same cost and may not last as long as a new one. This is why we do not sell compressor clutches. I recently did a conversion R67 to R689a on a Classis 955 Saab. I replaced the receiver dryer unit to no avail. From this web site I checked the expansion valve. The hose from the receiver-dryer to the expansion valve was plugged with particles from the old receiver dryer. I cleared this hose with compressed air, and had success. The hose connection to the expansion valve on my car had a small cone shaped screen filter that blocked the expansion valve from the contaminant. Converting from R67 to R689 Freon seems to be a subject that is in debate throughout the country as to what is necessary to complete the conversion. Many mechanics say that in-order to convert from R67 to R689 you should replace the compressor, receiver drier and expansion valve. It has been our experience with Saab AC systems that the original systems will convert to R689 without major complications. We do however suggest replacing the receiver dryer, all Oring's (included in the conversion kit along with the 689 fittings), the refrigerant oil and rid the system of all of the old oil by flushing the system. You must change the compressor oil from r67 to 689a oil. Other wise the system will not properly charge or run. Please be sure you dont let any non-condensables into the systems lines when doing the refrigerent swap.
Most of the issue with AC evaporators on the Saab 955 occur because of stess against the bottom of the neck where the expansion valve is screwed on. We have also seen issues where people install the pilot tube into the side fo the evaporator (from anti-frost switch) and cause damage in that manner. Replacement of the evaporator is the cure. The low side port is on the largest line and the high side port is on the smallest line. Typically the high side line is the smaller of the two lines and has the highest pressure running through it. The amount of freon needed in a Saab AC system is from 7. 5lbs to 8. 5lbs of freon to properly fill the system. When filling you can watch the site glass on the receiver drier or expansion valve to figure out when you have put in enough freon. Once the site glass goes from milky to clear then the system is full. Several things can cause your AC fuse to blow when turning on the Air conditioning. The most likely cause of a Blown AC fuse is a frozen or burned up AC Compressor clutch. When this occurs the heat from the burned up compressor clutch often causes the compressor bearing to seize up and burn the AC belt off. Compressor replacement is the only repair! Another reason can be a short circuit caused by the cable that runs to the compressor (In Saab 95-7559, it is a single and shielded one with blue plastic lining. This cable runs from a connector located at right upper side behind the front engine panel, directly down to the AC compressor). I solved the problem using isolating tape. Compressor was in perfect working condition and no dismantling was needed at all. On all the condensers you must be extremely careful when removing the hoses. When you remove the Upper and Lower AC hoses to the condenser you will destroy the condenser threads because the nut on the AC hoses are steel and the condenser threads are Aluminum or alloy. In just about every case the upper hose must be replaced with the condenser replacement.
This is quite common and this will cause you to have to replace the hoses (upper and lower). In some cases you may be able to clean out the lower hose threads to remove any aluminum that is in the threads PRIOR to installing the OLD hose on the new condenser. MAKE SURE your do this Prior to installing the hose. We cannot replace a condenser under warranty if you make this mistake! ! Leaking Hydraulic hoses can often be attributed to a leaky clamp which cause the hose to be able to be turned. You can repair some hoses temporarily by cutting a small 6/9 slice of the metal fitting out (being careful not to cut the hose) then put a adjustable hose clamp over the (now cut) fitting and tighten down the clamp. What happens here is that you cut just enough of the metal clamp out that when you put the hose clamp on and tighten it down that is basically creates a new clamp over top of the one that started leaking. This is a great quick fix and may last a bit but replacement of the hoses with new is the best long term solution. One of the most common problems with the A/C on the classis 955 is the failure of the A/C button. Switch Failures can often be identified by noting that the components will work only when the switch is held in manually. Replacement is the repair! On the Saab 955 79-99 testing for AC leaks can be done quickly. Simply go to the receiver driver which is located in the right fender well behind the battery and disconnect the two blue wires. Touch the metal of the two wires together and if they AC compressor comes on you know that the pressure in the drier is too low which tells you that you have a leak in the lines or the compressor itself. Most of the time if you have a leak in the lines you can see it because the line gets sticky or corroded around the area that is leaking. 5 Liter engines). Both components fail on a consistent basis on the 6985 and up 9555's. Compressor failure should be done by a professional technician only. Idler pulley failures can be identified by removing the belt and turning the idler by hand to see if the bearing has failed! The link below is a PDF that is designed to show how to dis-assemble your antenna assembly on the Saab 955.
This proceedure also applies to many other Saabs and should be about the same with only minor differences.