Temperature sensor idea: Is it probable?
Mr. Chips
Posts: 7
If anyone remembers the 1960's Chevrolet actually released a good vehicle called the Corvair.
It's an air-cooled flat-6 engine, and is really nifty to drive.
The problem is, the cylinder head temperature sensors are quite expensive, and only one side is monitored.
I'd like to use 2 modern sensors and connect them through an ADC of some sort to a STAMP.
I'd then like to use the STAMP to output both serial information to a logging machine that includes simple 'time since reset, plus temperature readings', as well as drive the gauge in the dash via DAC, I'd suppose (can the STAMP perform PWM on its output lines?).
Later in life, I'd like to add things like RPM (Simple pulse count / sec algorithm), system voltage, and perhaps drive a warning buzzer if the temps get too high or alternator fails.
So that's 2 sensors, tach, and Vin for inputs, and 2 gauges for serial for output.
I was thinking 7 bits would be OK for sensors and gauge drive info (128 positions on a 2 1/2 inch gauge would be fine, I'd think).
Given the appropriate chip, that leaves me up to 4 I/O bits free for buzzer / warning / ignition sense etc...
Anyone have an idea on what parts play well with the STAMPS? I'll be picking up a board of education in a month or so and will jump in to the world of microcontrollers from there.
It's an air-cooled flat-6 engine, and is really nifty to drive.
The problem is, the cylinder head temperature sensors are quite expensive, and only one side is monitored.
I'd like to use 2 modern sensors and connect them through an ADC of some sort to a STAMP.
I'd then like to use the STAMP to output both serial information to a logging machine that includes simple 'time since reset, plus temperature readings', as well as drive the gauge in the dash via DAC, I'd suppose (can the STAMP perform PWM on its output lines?).
Later in life, I'd like to add things like RPM (Simple pulse count / sec algorithm), system voltage, and perhaps drive a warning buzzer if the temps get too high or alternator fails.
So that's 2 sensors, tach, and Vin for inputs, and 2 gauges for serial for output.
I was thinking 7 bits would be OK for sensors and gauge drive info (128 positions on a 2 1/2 inch gauge would be fine, I'd think).
Given the appropriate chip, that leaves me up to 4 I/O bits free for buzzer / warning / ignition sense etc...
Anyone have an idea on what parts play well with the STAMPS? I'll be picking up a board of education in a month or so and will jump in to the world of microcontrollers from there.
Comments
Just don't drive fast in a Corvair. I have been in one (belonging to a friend) when the front end lifted (from aerodynamic lift) at about 80 mph. My friend held the wheel very straight and applied gentle braking, and the wheels soon touched down again. It's lucky we were on a very straight stretch of US 441 between Gainesville and Ocala, Florida.
Two months later my friend's wife was killed in that car.
No Corvairs for me, thanks very much.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
· -- Carl, nn5i@arrl.net
Post Edited (Carl Hayes) : 8/25/2009 12:09:14 PM GMT
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Don't worry. Be happy
Looks like they'll want 6 sensors (one for each cylinder) read and averaged for the guage drive. Then, 6 multicolor LED's that start blue and progress to green (normal operation), then orange/red as an overheat condition exists. This will end up being quite fun!
On the hardware side, I'll then have to find an ADC w/ several inputs I can multiplex control - let's say I use 3 bits to control the multiplexer (up to 8 sensors, then), 8 bit resolution. 8 bit output for the guage drive and 1 audible warning bit makes 20 IO pins used. With 4 remaining, that isn't enough for 3x3 pin LED warning (18 more IO pins) and voltage / tach monitoring.
It sounds like I may need two STAMPs. One on the engine for input w/ a high-speed serial link to another up front to perform output functions.
Sniffing the serial line will provide a method for a PC to store the data between the two units, then.
Do STAMPS have multiple serial ports? If so, I could use two stamps on the engine (one for voltage/tach/control, one for temp sensors), and then have one up front grabbing the data, driving the display, and providing common output for a serial logger (Which could be as simple as hooking up a thermal printer to the serial line).
As for 'aerodynamic lift', that's a common misconception. If that were the case, once lifted, the vehicle would flip up and point to the sky,CPUC says nothing's wrong with the cars, but 'murican drivers don't understand how to operate the vehicle - the biggest problem is people overinflated the front tires. 18-20PSI max (because they're not under load), so the front end can 'float' due to a very small contact patch. If only people knew (or read their owner's handbooks). It saddens me to see people injured, and I'm sorry your friend's wife did not survive her accident, but the car will respond to your inputs in a precise, quick manner - many folks still use these for 'autocross' racing, and they clean house.
If it were as you say, other cars with similar weight distribution (Porsche, VW) would do the same thing.· Well, Porsche anyway -- VWs don't go that fast.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
· -- Carl, nn5i@arrl.net
Are you sure it actually lifted the tires off the ground, and didn't lift the suspension to it's upper limits?
I'll have to ask some of the land-speed guys if they have the same problem - I think they use mostly the late model chassis.
Any idea what year the car was? 1965-69 are much more aerodynamic (The camaro was based on that body).
At 80mph, how much lift could be generated by a relatively square object that's not even 6 feet wide? That is an intriguing proposition for a small-scale wind-tunnel test of a model.
My theory was based on the fact when a _ moving at 80mph becomes a / after the front lifts up, not much will stop it from becoming a |, followed by &*^.- once the parts are all picked up.
Mr Chips: The Corsa cylinder head temp senders are probably some type of thermistor, a low-resistance thermal resistor that maybe a Stamp could measure with the right cap and RCtime, but it's a pretty electrically noisy environment back there. I installed type K thermocouples in each cylinder head last time I had the motor out. Never hooked 'em up, but the plan is that they will give a millivolt output that can be measured and read by a Stamp with some circuitry for a semi-calibrated temperature measurement.
Good news/bad news: I'd love to help you. I've been waiting for the right opportunity to jump in and design a bunch of Stamp instrumentation for my own car. BUT now just isn't the time. My wife and I are expecting twins in September and I'll be doing less Stamping and more changing poopy diapers. So all I can offer you now is enthusiasm and encouragement. Keep plugging and let us know how it's going and if we can help with suggestions. Another guy in the forum here is working on a speedo/odo for his Camaro. BTW, didja see where the founder of Papa John's pizza paid $250,000 to buy back his '71 Z28 Camaro? All over the web today. Google it.
erco
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
·"If you build it, they will come."
http://jalopnik.com/5350274/this-corvair-is-exactly-why-we-need-the-evergreen-747-supertanker
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
·"If you build it, they will come."
K-type is the way to go. Is them on my hovercraft, (2-cycle air cooled). It's REALLY too noisey to use anything else.
1967 Corvair Monza with a 140 HP·??· Sweet!! I'll trade you two of my hovercrafts for it.
Jim
Post Edited (hover1) : 9/1/2009 6:16:45 PM GMT
The front end lifted clear of the ground after the suspension reached full extension.· As the front end rose, the angle of attack increased, initially causing an increase in lift (positive feedback).· When the suspension reached full extension, it no longer helped raise the front end, and the front end stopped rising until the speed increased a little more, which it did because Dave kept his foot in it.· Soon there was enough lift to raise the front end clear off the ground, and it went up some more, until the AoA increased past the point of maximum lift; then it stalled, or maybe Dave was slowing rapidly (reducing the lift),·and the front end dropped heavily.· Felt like a stall to me, though there was no aerodynamic buffeting.· Some aircraft buffet, some don't.
Me, I'd love to have an old Corvair.· I think it's a really neat car.· I just wouldn't drive it faster than about 70 or 80.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
· -- Carl, nn5i@arrl.net
Post Edited (Carl Hayes) : 9/2/2009 12:35:39 PM GMT
If I wind up with the one I want, it has factory A/C, so the spare tire is in the trunk, and I'll be relocating the battery up there, too. That should reduce the chance of a flare like that. Freaky.
On pusher prop planes where the prop is rearwards of the center of gravity, I'd think the probability is higher to have a gentle lift 'n stall.
As for type K thermocouples, is there an easy method to interface SIX of them and still get readings twice a second?
If you are interested PM and I can give you the summit part number
It can also drive relays for fan control at a set temperature or for a meter I use the fixed 180 Degree model
Yes, I'm up for a project..
Specifically, I'd like to measure between 6 and 10 temperature sensors, voltage, and RPM and shove it out the serial port as a minimum.
Driving the factory temp gauge cycling through each sensor would be awesome.
Driving a small variable color LED for each cylinder is icing on the cake.
What I'm unsure of is how to do it. my BOE has arrived, and I'm working on getting a serial port connected on my PC (Can you believe it didn't have one? Sheez!). At that point, I'll dive in to the manual and start learning how to program a stamp.
This gives me a blinking indicator lamp and audio feedback based on input from one of the CD/s cells.
' {$STAMP BS2}
DIRS = %0000010010000001
Spk CON 8
x VAR Word
pin14 VAR Word
pin13 VAR Word
pin12 VAR Word
pin11 VAR Word
pin10 VAR Word
pin9 VAR Word
FOR x = 1 TO 100
HIGH 14
HIGH 13
HIGH 12
HIGH 11
HIGH 10
HIGH 9
PAUSE 1
RCTIME 14,1,pin14
RCTIME 13,1,pin13
RCTIME 12,1,pin12
RCTIME 11,1,pin11
RCTIME 10,1,pin10
RCTIME 9,1,pin9
DEBUG DEC x," "
DEBUG ? pin14,? pin13,? pin12,? pin11,? pin10,? pin9
HIGH 15
FREQOUT Spk,50,pin14
LOW 15
NEXT
Questions:
With the separate 'HIGH' commands, do I need to pause for a millisecond for the capacitor to charge?
Can I combine 'HIGHS' in a single command via a bitmap of some sort?
Can I combine RCTIMEs to all read in parallel (probably not)?
I'll have to convert the sample counts to resistance, then convert that to temperature (Pending on sensor used). Now I need to buy a bunch of close tolerance resistors and caps - would ceramic caps be better for a high heat environment? I'd think so, but I'll probably end up using ribbon cable to a fiberglass insulated harness on the engine.
DS2760
____$WMc%______
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
The Truth is out there············································ BoogerWoods, FL. USA
I figure the only reason to upgrade to a more powerful STAMP would be to add the tachometer function, but I don't wan the tach function to kill the idea of the temperature gauge drive etc..