need cheap tach

Karl Townsend fired this volley in news: snipped-for-privacy@4ax.com:

Karl, There are all sorts of small analog tachs available in auto stores for cheap.

I installed one on my diesel tractor using a hall effect sensor to do the triggering.

I know it's not digital, but please consider that the digital ones aren't all _that_ accurate, either.

As far as spraying goes -- are you using a PTO pump? If so, volume will more-or-less match engine speed, regardless of the _exact_ speed you go.

On a PTO pump, you control volume with flow restriction.

LLoyd

LLoyd

Ask the tech. He can probably tell you exactly what you could add to a new tach to make it as good as the old tachs.

Dan

Have you looked at gps receivers? The one with some augmentation as WAAS might be accurate enough. There is a thread on sci.electronics,design labeled

Testing the Dealextreme ET411 GPS module

I would think this is a common problem for farmers and Jan might be interested in developing a system for accurate slow speeds for farmers needs.

Dan

" snipped-for-privacy@krl.org" fired this volley in news:8c560f45- snipped-for-privacy@w24g2000vby.googlegroups.com:

GPS is useful for maintaining a good pattern, but not really very good for manually-controlled tractors. The GPS has to drive to make it accurate.

For the most accurate path control with a manual tractor, one uses a foam dripper to mark the lines. Dyed foam will be visible for days, unless it rains hard.

As I said before, the problem of matching application rate to coverage was long ago solved by using PTO-driven pumps, the volume of which exactly matches the speed of the tractor (assuming the same gear and not below the critical "self sealing" pumping speed, of course).

One can calculate gallons-per-acre almost to the quart with a pto pump in good condition. Within fairly wide variations, speed doesn't matter a whit.

Of course it takes calibrated nozzles, a known boom width, and all that other flow-related crap. But once you have the equipment in place, you make one run over a field with water, figure your consumption, and develop your concentrations (again, within acceptable ranges) on that.

If the concentration is too low because the volume is too high, you reduce the number of nozzles or their size. And vice-versa.

This problem was NAILED decades ago.

Lloyd

LLoyd

Rockwell has been flogging systems for farmers for years. Dunno how expensive they are.

why not cut the old one open and change the battery? it can't be that hard - I've changed the battery on some other "permanent' items before with some success

Can you crack the case open and replace the battery inside?

Jon

I would disagree with you here. I use 3/8 to 1/2 of lable rate on most every product. That leaves no cushion for error (saves me over $2K a year) if you're trying to keep application rate variation well under

+/- 5 percent you got to keep everything constant and be very observant for any sign of wear or plugging. Another huge item is to exactly finish the tank twenty feet after the last row. 50 RPM will raise the pressure 2 PSI while hardy changing speed. or you're already 5% higher on field rate. A primary screen plugging will drop you 1 or 2 psi if you're positive its not RPM, you can spot it right away. I'm also logging pump and nozzle wear from day to day and making minor gal/acre adjustments. Again if you keep everything constant, ths is easy to spot

most folks don't believe me when i tell them farming is more techical than they know.

karl

Karl Townsend fired this volley in news: snipped-for-privacy@4ax.com:

It certainly is now. With that, I'll agree. With the other, we'll have to disagree. My opinion, of course, but I think if you get variations as wide as you say for any reason other than nozzle erosion and pump wear, something isn't right. Slip in the drive train, worn pump rollers... something. Is yours a big field machine with an automatic tranny? Torque converter maybe doesn't lock up completely?

Everybody uses less than the label rate, if they can get uniform coverage, and if it works at those levels and prevailing weather. If I'm spraying Basogran, I'd _LIKE_ to use 1/10th label... but it doesn't work that way. Then there's Sonar for the pond and irrigation ditches...

Karl, I don't have a "real" farm, just 20 acres in turf grass sod. So YMMV on "real" crops. My numbers have to come out close, too. Sod sells for cheap, unless you're the cutter/distributor.

Lloyd

I'm not sure why a filter would be required- looks like you could reduce the sensitivity using shielded wire and maybe a single turn around the ignition wire. No?

Best regards, Spehro Pefhany

I'm going to play more with this idea. the vendor had me cut the lead down to one inch and use just a hook, no joy. I think I'll try to increase the distance by wrapping a gob of elctrical tape around the plug wire.

I assume you're thinking AL foil. Which wire would you wrap, plug wire or unit pickup lead, and should it be grounded?

Karl

Is the pickup wire shielded now? Shield grounded?

Best regards, Spehro Pefhany

A classic dodge would be to pass the sparkplug wire through the center of a ferrite toroid upon which a few hundred turns of fine wire had been wound, forming a simple current transformer. The fine-wire winding would be connected to a bit of coax which would carry the signal to the tach. The winding can be shielded (so long as the shielding does not form a closed metallic loop).

This will sense the current drawn by the spark, not the spark voltage.

Joe Gwinn

yes and yes, all but the last one inch. The tech. had me cut it down in an effort to correct the problem.

The guy at Tiny Tach is GREAT. He's making me two custom tachs with filters. So, I'm good for five more years. I'll worry about it then. or, with luck, I'll be retired and fishing full time.

Karl

...

WHAT, Agreeing to disagree without yelling and screaming and calling each other names? I guess we're out of step, its not done this way anymore :)

Karl

Karl Townsend fired this volley in news: snipped-for-privacy@4ax.com:

Lloyd

Karl, how about a photo tach reading impulses directly off the PTO? Small spot of reflective tape and mount the sensor and you should be OK.

Hope you have better luck than me with the fish. The bite seems REALLY screwed up this year.

Karl might even be able to use a bike computer for the job when calibrated. I've read about people that have fitted them to disc/drums and they worked fine but having the pick-up on the propshaft was too fast. That was for car use and I would suspect a tractor and the PTO to be somewhat slower so may be OK.