Mill Speedo Tach

Professorwiz

I was looking at the Basic Stamp project, Mill_Speedo that uses the Melexis 90217 crank sensor.· Has anyone converted this for use with the SX chip?·

Professorwiz

Opps forgot to add, the original posting / data is here
http://www.parallax.com/html_pages/robotics/machining/RPM_display.asp

Thanks,
Russ

Capt. Quirk

Yes I have, but it has been modified to fit· my needs. The biggest problem was the SubRoutine LCD_Put_RJ_Value, Bean & JonnyMac both provided code for it and you can find their examples in the SX thread index.

What are you planning on doing and with what type of lcd?

Also, the hall sensor works great, no problem with the SX.

Bill

Professorwiz

Well actually I wanted to use some really cool 4" tall 7 segment displays, that have 4 segments connected to them.· I have 2 projects in mind, one is I have a largesh (for Hobbiest) cnc machine I'd like to put a spindle speed display on, and another is I have a .90 nitro motor that was converted to spark ignition with electronic timing.· I was wanting to just make an RPM display for that while bench running it in, or perhaps a temp / rpm display that would switch between the 2.· Lots of idea's but not enough smarts yet.·

I did read the Parallax help portion, for the LCD display and I didn't understand it.· I know understand that the serial out doesn't do exactly the same as the Basic Stamp did, and only does one character at a time, but I'm missing something on that.· I'm not sure if I'm biting off more than I should or not at this stage.



Russ


Post Edited (Professorwiz) : 8/6/2007 11:07:01 PM GMT

Bean

Russ,
Are these the displays you purchased from me ?
Did you get a circuit to drive them ? I couldn't find the one I had used, but I could pencil and scan a schematic if you need it.

Bean.

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Teacher: What is the difference between ignorance and apathy ?
Student: I don't know and I don't care
Teacher: Correct !
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·

Professorwiz

Bean,

Yes these are the ones I got from you! Thanks they look great, these should be really cool.· I would very much appriciate any kind of pencil schematic from you!· They should be very neat on both projects.

Russ

Capt. Quirk

I have code for a Parallel LCD that displays RPM's and Head or Exhaust temp (or both) for a type K thermocouple and MAX 6675 CJC IC's. You can have any part of it or all of it, if you want it.

Bill

Professorwiz

Bill,
That is very generous of you, yes I would love to get your code from you.· I just checked out that Maxim part, wow up to 1000C temp reading.· That's pretty hot stuff!

Russ

Post Edited (Professorwiz) : 8/7/2007 9:07:40 AM GMT

Bean

Russ,
· Here is the drive circuit I used for the 4" LED displays.
·
· I have alot more of these displays. If anyone want to buy some they are $10 each + S/H. Just email me if you are interested. I also have 2.5"($7.50) and 1.8"($5.00) (the 1.8" do not need the high voltage drivers, they will work from +5V). They are all multiplexed (only one digit on at a time).

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Teacher: What is the difference between ignorance and apathy ?
Student: I don't know and I don't care
Teacher: Correct !
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com


Post Edited (Bean (Hitt Consulting)) : 8/7/2007 12:15:43 PM GMT

Professorwiz

Bean,

I have a question on your schematic.· for R3 it shows a 4K7, I'm unfamiliar with that nomenclature.· Could you explain what that means.· Sorry to have to ask you something I'm sure is simple.

Russ


Post Edited (Professorwiz) : 8/7/2007 12:34:52 PM GMT

RDL2004

Professor,

The letter K indicates where the decimal point is. I think this method·of specifying the value·comes from parts that are marked with numbers instead of color stripes - it's harder to rub the whole letter off to where it becomes illegible vs. a single dot.

The letter used gives the multiplier, R is used as zero, K is x1000, M is x1meg.

So 4k7 is 4700 ohms. 100R would be 100 ohms. 3M3 would be 3.3 megohms.

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- Rick

Professorwiz

Rick,

Thanks, I knew it had to be something simple. I appriciate you taking the time to inform me.

Russ

Bean

Russ,
Rick is correct. The "K" takes the place of the decimal point. When schematics get faxed or copied it is very easy for the dot to go missing. So a 4.7K resistor looks like a 47K resistor. Using the "K" for the "." Makes it less likely to get screwed up.

I have to thank our friends in the UK for this idea.

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Teacher: What is the difference between ignorance and apathy ?
Student: I don't know and I don't care
Teacher: Correct !
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com
·

Capt. Quirk

Here is the code I was talking about. Youn will have to convert some of it for use with LED's, but it's a start.

I would recomend placing the thermocouple as close to the spark plug seat as possible. A reading from under the spark plug of 300·degrees F or 149 degrees C, is optimal. You may be able to find a ready made TC to fit under your spark plug (even if it's a 1/4-32) from EGT

Buy the smallest neodymium magnets·you can, it will still be more than enough for the Melexis Hall Sensor

Good Luck

Bill


Post Edited (Capt. Quirk) : 8/8/2007 4:11:16 AM GMT

Professorwiz

Bill,

Thanks for very much for posting your code.· I appriciate your time and effort.·
The magnet I'm going to use is the one Parallax sells #605-00006.· I'm going to try to use the existing magnet on the crank that the electronic ignition system uses first though. ··Reading though the·mfg sheets on this trigger though, it shows that you can pickup the edge·without a magnet, because the denser material interuppts the magnetic force around the·sensor.· Have you tried this?

Russ· <!-- product category -->

Capt. Quirk

Regarding the magnet on the crankshaft, use a small compass·to determine its pole (needs to be south). For the gear tooth sensor, it requires a magnet to be glued to the back of the sensor. South side facing the back side of the sensor. (I have found the melexis to be more sensitive than other hall sensors that were supposed to be, but I wouldn't trust no magnet at all)

It's funny to me that you mentioned the gear tooth sensor, just yesterday I modified a 48t gear and cut the teeth off to make it a 24 tooth gear (1 tooth for every 15'). I fitted it to my ignition test stand and glued the magnet to the sensor·and then to my dismay, it was a stainless steel gear. OOPs.

<<== Bill

One other thing, I have tried tape magnets with the melexis and it did recognize it, but the weak magnetic field produced fluctuating results. I think it's best to glue the magnet to the back with epoxy or CA and Kicker.

Also, an easy way to mount the sensor is to use a small carbon fiber tube·or·brass, copper or aluminium·(1/4" to 3/8" dia).· Bend the sensor 90 degrees and glue it with epoxy so the numbered side of the sensor faces out. Then make a bracket with a set screw, to hold the tube and adjust the distance from the magnet or gear.

I will post some pics tonight.

Post Edited (Capt. Quirk) : 8/8/2007 5:04:03 PM GMT

Professorwiz

Bill,

I'm still going though that program! Thanks for all the comments in it. It'll take me a while to digest it all.
Bummer about the gear, too bad it wasn't at least 400 series stainless!

Russ

Capt. Quirk

Russ,

Use DEBUG and walk through the subroutine "LCD_5_DIGITS" to see how it works. Originally I called "LCD_OUT" from LCD_5_DIGITS and had problems with __PRAM1, So I just added a LCD_OUT routine to the bottom of the routine.

Also here are the Hall Sensor pics on a Zenoah GT80.


Post Edited (Capt. Quirk) : 8/12/2007 9:31:21 PM GMT

Capt. Quirk

One other thing, there are 3 or 4 types of 1/4 - 32 spark plugs. Which one are you running and what %'s are you running of nitro and oil, and type of oil if you don't mind.

Thanks

Bill

Professorwiz

I'm running Amsoil 50:1 with gasoline, midgrade. The plug I'm using doesn't have any markings on it. It the one BME sells with their engines at a mear $28 each.. Ouch.. The ceramic breaks if you sneeze at them. I've already purchased 2 more besides the one that was in the motor and I'm on the last one. You have a good place to buy these, or perhaps a little better made?

Russ

Professorwiz

Bill one more question, I take it that's a motor of your own design, are you able to buy just the jugs off the Zenoha or did you scavage those?

Russ

Capt. Quirk

No that's a real Zenoah model airplane engine. (edit) I just needed to run multiple hall sensors)

Are you running gasoline, so that you can race with the Zenoah G230's,·260's and·Quickdraws etc. ?

If so how do you get around the piston port only rule?

Bill


Post Edited (Capt. Quirk) : 8/13/2007 12:49:55 AM GMT

Professorwiz

Bill,
No I'm not doing any racing.· I wanted a good running gasser for my Helicopter.· I've got a Raptor 60/90 that I use for aireal photography.· Using a nitro motor makes me keep moving around to get out of the smoke.· The nitro exhaust is also very corrosive, it eats the finish off the camera.· I've run a tube all the way back to the rear rotor to help that out, but I don't want to hang my Canon Xt unless I can't get the gasser working.· With the gas motor I can also get up to 40 min. a tank of flight time, with the nitro I get 15 min a tank.· That's barely enough time for me to get up align good enough and take a shot or 2, moving about to keep out of the smoke and all.· I just need to quit being cheap and get a good gasser heli like the Preditor that's made for this work, but I haven't had a paying job yet.· I've heard there are tons out there, but sorting all that out has taken up my entire summer flying season.. Now of course I'm involved with the Basic Stamp, and SX chips.·

Capt. Quirk

·Really Nice Picture



Over 10 yrs ago I had a few chances to work with·a guy that was using the GT74 Zenoah (an earlier model of the GT80) in his heli. He was looking for more power back then.

I can see why you need the 50:1 amsoil, but·I think it's to big of a risk for your investment.

Bill


Post Edited (Capt. Quirk) : 8/13/2007 1:28:33 AM GMT

Capt. Quirk

I wanted to show you my Ignition test stand. Soon I will have a degree wheel and timming light added to it. It's just a sewing machine motor and a Dayton speed control.

Capt. Quirk