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Post by racket on Jul 31, 2014 17:37:52 GMT -5
Hi Guys
Whats the latest on tachs for very high rpm of >100,000 rpm up to ~200,000................anybody found a simple solution thats hopefully "off the shelf" ??
Cheers John
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alan
Member
Joined: August 2010
Posts: 36
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Post by alan on Jul 31, 2014 18:20:58 GMT -5
A while ago my friend, who is an electrical engineer, took Sal's tachometer design, which did work, and modified in a way to make it a little better and he added an over-speed protection circuit which incorporated a latching relay. We got about 10 boards printed out and I have all the components, but he ended up moving away and we lost touch. My friend, Roger, said, in theory it could sense over 120,000 rpm. It might be possible to sense the high rpm range you are looking for John. I still have everything, and the cost per unit ended up being around $40 with shipping within the US. I am afraid I still do not have the time to dedicate to completing this project. So if someone would like put one of these boards together and do some testing, then I would be willing to ship a board and the components out. I know it's not "off the shelf", but it is an easily affordable option.
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wolfdragon
Senior Member
Joined: April 2011
Posts: 287
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Post by wolfdragon on Aug 2, 2014 12:53:08 GMT -5
I would have to see the schematic, but it looks rather brute force in its design.
As long as you don't outrun the counters/clocks, then you won't have any problems.
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Post by pictsidhe on Aug 2, 2014 13:09:26 GMT -5
I'm looking into electronic stuff I can make and sell at the moment. As for tachos, Since pickups are a bit of a pita to install, I'm pondering an acoustic pickup system. A small hole in drilled in the casing where it is swept by blades, pipe/tubing connects this port to a sensor. The blades create pressure variations. The signal is cleaned up, divided down and fed to an off the shelf low speed tacho or converted to a voltage for multimeter to read. I don't have a running turbine to test this but do have a turbo car. It should work on power turbines too.
I'd be very interested in knowing the max and min RPM and number of blades that people will want to measure. Eg, KP31 turbo, 5+5 blades, 300,000RPM that's a sensor pulse frequency of 50kHz, is anyone likely to go much higher?
A programmable divider adds complication, the more steps the trickier. I'm still pondering the best way implement that.
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Post by finiteparts on Aug 2, 2014 14:51:00 GMT -5
All, I am sure some of you have seen these gauges that are available from Garrett... www.turbobygarrett.com/turbobygarrett/accessoriesYou maybe could get some ideas from the downloads on installing... www.turbobygarrett.com/turbobygarrett/sites/default/files/accessories/781328_Speed_Sensor_Kit_Installation_Instructions.pdfUnfortunately, they are quite proud of them and the cost is pretty steep... www.atpturbo.com/mm5/merchant.mvc?Screen=PROD&Product_Code=ATP-ACS-020&Category_Code=BCSBorg Warners offering is cheaper, but once you add their display cost, it's no better...which may not be a big deal if you were wanting to build your own display... www.full-race.com/store/efr-turbo-accessories/borgwarner-efr-turbo-speed-sensor-kit.htmlwww.full-race.com/store/efr-turbo-accessories/road-rage-gages-sbt-kit-speed-boost-temp.htmlThe common thought is since the compressor wheel is Al, these sensors can't be variable reluctance or Hall effect, so these RF sensors seem the likely candidates...I ran across these when I was looking for eddie current proximity probes for watching shaft dynamics. I haven't check on prices or the required signal conditioning, etc... www.motionsensors.com/speed-sensors/rf-speed-sensors.shtmlHolsets VG turbos usually have a provision for a speed sensor since the ECU has to command the nozzle position since the turbo could overspeed if there was no way to watch the shaft speed. Commonly, the shaft has a flat milled in it just below where the sensor is mounted in the center housing. This might be an easy mod on existing turbos, except for the requirement to re-balance the shaft. There area few of them out there that have the sensor mounted to the compressor housing just like the other two manufacturers arrangements, which suggests that maybe some Holsets have a eddie current style speed sensor(?). I thought the sensor in the center housing was a variable reluctance style, but I just ran out an checked one of them and they have three wires and the plugs looks identical to the Borg Warner sensor shown above. Does anyone have any info on them? ~ Chris
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Post by pictsidhe on Aug 2, 2014 15:43:33 GMT -5
probably capacitive sensors, they aren't cheap edit: I'm referring to the Garrett and Borg-Warner ones. Dunno about the shaft sensors.
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Post by racket on Aug 2, 2014 18:27:11 GMT -5
Hi Guys Mmmmmm, things ain't looking good for a cheap off the shelf unit , the Garrett ones count the blades and you adjust the tach for the number of blades on the comp wheel, but theres precision hole drilling etc, and the tach gauge is pretty crude and small , probably OK for auto use where the "extras" with the unit can be utilised, but for us we only need to read the rpm and then only for a limited time . The black/white comp snout has sorta stood the test of time for us DIY'ers , my old TNC tach came with a remote sensor that could be easily mounted on the comp cover whilst the readout unit was mounted somewhere easy to see during a spoolup , but unfortunately they're not made anymore , the "replacement??"..... www.fromeco.org/products/05frctnc/ doesn't appear to have the same provision :-( The RC micro turbines can use magnets and hall effect sensors but thats not so easy for us especially if using boreless Garrett GT turbo compressor wheels . I guess if anyone wanted to make tach units, one capable of "reading" a black/white painted comp snout would be ideal especially if the sensor came with a few feet of wiring back to the tach, its that spoolup rpm that I've found most valuable to know, its a bummer when you don't have a tach and you rely on "the sound" to determine if the engine is past self sustain and able to idle without the starter power .................all of the inexpensive tachs I've been able find are hand held units which are useless during a spoolup when I don't have enough hands as it is There have been some tachs with sensors that required being fairly close to the black/white snout , but the interruption to airflow from their mounting is a concern , we need something that can be mounted at least 2"-3" from the snout. LOL......I'll keep searching :-) Cheers John
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Post by pictsidhe on Aug 2, 2014 20:46:45 GMT -5
I'm going to have a stab at an acoustic pickup and see what happens. It'll have a minimum RPM dependant on your well I can process it's signal.
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Post by finiteparts on Aug 2, 2014 22:53:16 GMT -5
Since I have an older Holset HE431VE with the milled shaft pickup location, I found out that it is a variable reluctance type by looking at Cummins repair manuals (and a Mack V-MAC IV manual). The patent literature shows that Holset (and others) are using eddie current speed sensors since about 2006 (first published 2003). The repair manuals only state that you should not use a multimeter or other device to test the speed sensor since the sensor contains internal circuity that will be damaged, which is consistent with an eddie current type pickup. So it is likely that the newer turbos and the HE341VEs that have the pickup on the compressor housing are using a eddie current speed sensor. Additionally, here are a few other resources on similar turbo sensors. www.micro-epsilon.com/download/products/dat--eddyNCDT-turboSPEED-135--en.pdfwww.jaquet.com/site/assets/files/1201/flyer_turbotach_a4_en.pdfMy guess is that the Garrett and the Borg Warner are also eddie current speed sensors. ~Chris
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alan
Member
Joined: August 2010
Posts: 36
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Post by alan on Aug 2, 2014 23:53:37 GMT -5
Here is the schematic. This was designed to work with black and white painted spinner. It can also use the flats on the comp nut to calculate rpm, you just need to change the jumper position.
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Post by pictsidhe on Aug 3, 2014 8:16:43 GMT -5
I still think having a sensing setup that runs a conventional tacho would be best, there's a lot of ready made tachos out there for cheap or in your junk pile, they just need a lower frequency than a turbine shaft spins at. Alan's circuit has a very handy takeoff for a normal tacho in the form of the divider jumpers. An extra 4018 to add an optional x10 could be useful though. A lot of car tachos are 2 pulse/rev triggering, bike ones more often single pulse/rev. If my acoustic sensing idea doesn't pan out, I just need to change the front of the circuit, the rest won't care what is making the pulses.
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nersut
Veteran Member
Joined: September 2012
Posts: 223
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Post by nersut on Aug 4, 2014 7:54:57 GMT -5
A while ago my friend, who is an electrical engineer, took Sal's tachometer design, which did work, and modified in a way to make it a little better and he added an over-speed protection circuit which incorporated a latching relay. We got about 10 boards printed out and I have all the components, but he ended up moving away and we lost touch. My friend, Roger, said, in theory it could sense over 120,000 rpm. It might be possible to sense the high rpm range you are looking for John. I still have everything, and the cost per unit ended up being around $40 with shipping within the US. I am afraid I still do not have the time to dedicate to completing this project. So if someone would like put one of these boards together and do some testing, then I would be willing to ship a board and the components out. I know it's not "off the shelf", but it is an easily affordable option. Hi Alan I am interested in the tachometer board, could you send a unit to me? I live in Greenland, city: 3900 Nuuk I can pay the bill from PayPal. I could put the unit together & test it on my DIY gas turbine & post the results here. Cheers Erik
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Post by finiteparts on Aug 4, 2014 19:52:08 GMT -5
All, the link provided below shows that they also sell a converter box for the Borg Warner speed sensor that might make things a bit more manageable... roadragegages.com/tss.htmThis puts the sensor and converter in the $200 range...plus converting a gauge to read the 0-5V scale would be relatively easy. Another link that actually tells us that Borg Warner is using an eddie current type pickup. blog.autospeed.com/2007/09/28/turbo-tech-developments/~ Chris
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ashpowers
Veteran Member
Joined: February 2011
Posts: 207
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Post by ashpowers on Aug 5, 2014 13:05:07 GMT -5
This is actually the approach I took with the GT Control board I made several years ago. However, I was using an IR LED as my light source and unfortunately that had issues out in sunlight. Using a diode laser and an appropriate phototransistor will work significantly better. Diode Laser: ($13) www.quarton.com/download/9/Phototransistor: ($0.67) www.fairchildsemi.com/ds/KD/KDT00030.pdfHowever, the one difference I was going to make was instead of painting parts, I will be machining a new compressor nut that will have a hole bored through it radially that each side is tapered outward from center to the circumference of the nut in order to produce a window that equally splits the window time 50/50. This hardware arrangement may very well not even need a schmitt trigger to clean up the signal and could be sent directly to the F-V converter or directly to a multimeter that measures frequency. However, it is always a good idea to try and clean up signals as best as possible and a schmitt trigger can be biased such that it wont accept stray signals or noise. None of this is expensive stuff to make. Even adding a configurable decade counter to divide pulses like what is used in that board above will only run you $0.56, LOL. All of this can also be built on a breadboard. I've actually come across something that I will be divulging in the T04 thread regarding this and a completely new engine control system that I'm working on... Something VERY nice and pretty affordable that I'd be happy to share with the group.
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alan
Member
Joined: August 2010
Posts: 36
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Post by alan on Aug 7, 2014 5:28:18 GMT -5
nersut,
check your messeges, I sent you one.
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