Newbie here building a dynamometer, daq, sensors, etc, help

[fastline]

OK, to be honest, my brother is the electronics and computer guy, I am the power grid guy and the motor head. I am doing research to build a brake dynamometer. This will require multiple temp sensors, tachometers, and a few other basic instrumentation. We want to use mostly IR temp sensing for simplicity of test vehicle setup. We would also like to use IR sensing for tach pickups as well.

I guess our first objective is to determine how to make these IR critters? They seem a little to costly commercially since we will need around 5 temps sensors, and 4 tach sensors. Temp range will be 50-250F, and 500-1300F, and the tachs will need good precision and 0-5000 rpms or ppm. So can anyone help with design of these little guys component wise?

We are also a machine shop so building the holder devices for potting and such should not be an issues. The next order here will be building the daq system but we will save that for another thread I guess.

 

[3v0]

The tachs should be easy and inexpensive. There are numerous articles on the web regarding the construction of tach. In general they either count pulses or the time between them. Often triggered by optical.

Regarding the optical temperature sensor this may help: how sensors work - infra red temperature sensor

 

[fastline]

As I understand it, the circuit is configured with an RX and TX diode, one emitting IR rays, one receiving them. The RX diode emissivity will be set at the proper range depending on what type of material is being tested for temps. the range would be set to a small band so as to only react to certain reactive wave forms associated with delta T.

Is this right so far?


So the main circuit and components are basically the same but the "tuning" portion of the RX diode is what is actually tuned to react to wave forms in certain ways. ?

 

[3v0]

First I am guessing you need rapid temperature readings. If not there would be easier ways to obtain temperature.

I looked at 3 pages of google results but did not find any circuits. The search was far form exhaustive but I think in may indicate it is not as simple as one would hope. Could even be cheaper to buy the commerical units. But we do not know that yet.

From the linked page.

The intensity of an object's emitted IR energy increases or decreases in proportion to its temperature. It is the emitted energy, measured as the target's emissivity, that indicates an object's temperature.

IR/Heat is emitted by everything above absolute zero. The temperature is indicated by the intensity of the IR emitted. You do not need an emitter.

At this point I am in over my head on the IR temperature. (but that is where the fun starts) Any always if anyone knows more then I do please speak up.

I looked at mouser and found 980nm phototransistors for under 20 cents. https://www.fairchildsemi.com/ds/QS/QSB363.pdf

The important part of the datasheet are the graphs.

I would guess you need a good (the right) op amp between the phototransistor and the microcontrollers ADC. The phototransistor should be keep at a constant temperature or you need to measure its temperature and adjust based on that.

Questions you need to answer. What material will be emitting the IR, what temperature range will be measured, and how mahy decimal places do you need.

Please indicate C or F.

 

[3v0]

https://www.kennethkuhn.com/students/ee431/text/phototransistors.pdf Much of this text is regrading binary light detection. The last paragraph and schematic are analog. A place to start.

 

[fastline]

I am certainly open to other possibilities for temp sensors. We want to read temp on the outside of th the exhaust which can get upwards of 1300F. Should be looking at some type of contact sensor to make like easy? We can sure be in contact with the test piece so if that will better our accuracy, we can go another route.

I do need IR sensing for at least one tach though. I find IR sensing rather interested and could really come in hand in the future.

Would you think thermocouples (can't remember their ranges) work for these temps I noted above?

 

[3v0]

In collage we had a thermocouple we dipped in liquid brass to measure its temperature. So the temperature range is not a problem. But the IR will give the best response and I find it interesting if that counts.

As I said earlier the optical tach is almost a no brainer.

Where do you live and what is your timeline.

 

[fastline]

I am in Kansas and we probably have a couple months before we have to execute something. My immediate goal was to determine which sensors to use for what and possibly just make them since many sensors are very costly yet cost peanuts to build. We could probably find all sorts of uses for these little guys if they are truly accurate.

I am starting with sensors because I will need to know what I will use when selecting a DAQ system. There are many, very technical parts to this build so we will take it one part at a time I guess.

I will need to tach sense my load roller, the back axle of a vehicle, and use an inductive loop on a plug wire for getting a pulse from the engine for rpm. We may also opt to pickup the actual crank sensor of an engine so I can compare crank sensor data to plug wire data to get my ignition advance.

Temp sensing will be for aiming at any part of the engine we might be concerned about, as well as the EGT from the outside of the pipe, and if there is not a water temp sensor, we will need that data.


I guess if we can learn how to make these IR sensors and configure them to our needs, we could simplify our sensor builds.

**broken link removed**

Here is something I found yesterday that is interesting. Probably does not apply to temp sensing but I don't have much experience with IR sensors.

 

[fastline]

I am in kansas and we have around 2 months before we really need the sensors.

I tried to post two other times and my reply was deleted. Did I do something wrong? I did include a link to some IR sensor info... Not sure.

 

[3v0]

Once in a while posts seem to go into the vapor. Not sure why.

Given the short time frame it would be best to look into what you can afford in off the shelf parts for the temperature sensors. It could be as easy as hooking an opamp up as in the schematic I found but there is no way of knowing. Then one would have to calibrate it which would require a know good temperature sensor. You did not answer my question about the temperature sensor requirement.

Can we turn my pickup on you dyno when they are finished

 

[fastline]

Once in a while posts seem to go into the vapor. Not sure why.

Given the short time frame it would be best to look into what you can afford in off the shelf parts for the temperature sensors. It could be as easy as hooking an opamp up as in the schematic I found but there is no way of knowing. Then one would have to calibrate it which would require a know good temperature sensor. You did not answer my question about the temperature sensor requirement.

Can we turn my pickup on you dyno when they are finished

We are certainly willing to buy assys to get over the hump but all the sensors I have found are $300+ each and that makes little sense on the budget project. We have a decent budget on this build but buying several sensors at 300 each will surely put us out.

I am not sure which question you had on sensor equipment but we will measure only steel and Al. The engine ranges will be 30-300F, and the exhaust will be roughly 400-1500F. +/- 1-2% is our accuracy window. I am not sure what you mean by off the shelf parts and ad an opamp. Isn't there basically a RX IR receiver, some basic resistors and such, and an opamp? I am not sure yet how we tune the emissivity yet though.

Our first dyno will be smaller to get the hang of it. ATV/UTV, motorcycle stuff but we will build a car version within 1.5 yrs from now. We will run both. Once the car dyno is done, you are more than welcome to bring it on! We will build for pretty high HP. We are working on custom water brakes right now. That is the most economical way to control big power like diesels and NOS. Eddy current will require over 10K just in absorbers.

Where are you located?


Because of the complexity of this build, we are sure looking for a little help in all this in return for some freebie tuning. I think the biggest problem is the chip programming to control our brake. We must be able to create pre-programmed tests like sweep test at a certain accel rate, stage and hold where the motor will come up at 500 rpm increments and hold for 1sec each, etc. All of this will depend heavily on how we opt to control the water brake. We are surrounded be engineers here but none with specific expertise in this. We are considering running a water pump to the brake with a VFD and controlling with the VFD with a processor. Just not sure yet

I contacted our local college where we used to be involved in their race program for fun 10 yrs ago. They did not even know what the difference was between inertia and brake dynos. Needless to say, dead end there. We will get there but looking to push the design time frame a bit. I am an engine guy with 15yrs experience in the field. We actually patenting a head design right now. Just have to have the data to help in fine tuning.

 

[Nigel Goodwin]

Once in a while posts seem to go into the vapor. Not sure why.

As a new user his posts are subject to moderation, so don't appear until approved.

That's why there's almost no spam here, I generally delete it before it can appear.

 

[fastline]

By the way, one of our largest obstacles is how to balance our load roller. We REALLY need to better understand balancing and possibly just build electronics for this because that will get STUPID expensive. Our lathes are not big enough for the roller but I have people to turn the OD once build but I will need to balance it for 5000rpm. At 200-300lbs, I don't need it trying to walk out the door.

I was hoping we could come up with a V block design to fixture the roller and use load cells or something to determine balance. Not sure how this works though. We have plenty of other balance problems around here so learning this would really help.

 

[3v0]

Look for my PM.