Tachometer design

Thanks Steve?????? Are you blokes trying to send me broke and divorced?????

Now I've got another 2 ideas for things to make.

Regards

Dave Tointon

 

 

To Dave Tointon:

 

Hi Dave,

Try Elektor Electronics (www.elektor.com) they often have beginer projects for PIC.

Other sites to try are:

http://www.microchip.com and their outlet http://www.microchipdirect.com

 

and make friends with people like Les and I, who have experience with microcontroller design.

i must however point out for those of you who now have a raised interest in developing your experience and hopefullly own projects, that this is not a cheap hobby.

 

you will need;

Variable Power supply ~£60 - £300

Multimeter £10 - £100

Breadboard £4-£8

Test Leads £2

Oscilloscope (very difficult to find problems without) £200 - £2000

MPLAB (good starting point for code creation and debug-----it is FREE).

 

nice to have

Function generator ~£100 - £1000

Frequency/period counter ~£150 - £1000.

Schematic/PCB capture ~£150 - £6000.

 

So if the cost of setup has not yet frightened you, welcome to the world of Electronics where we all (Electronics Designers) have an absolute passion for the field.

@Dave T,

 

Here are links to other websites that may help your education:

 

http://www.electro-tech-online.com/  This site is a general chit chat forum where you can pose questions and expecta reasonable if not good answer..

 

http://www.talkingelectronics.com/te_interactive_index.html This site is an education site covering many aspects.

I don't think this is fair - we should stop winding Dave up!

 

Because in the past I've done quite a bit of analogue electronics design, my 'indoor' workshop (yes I'm actually allowed one by SWMBO) looks somewhat intimidating at first glance - well it does when it's tidy. Yes you can spend a lot of money on stuff like this, but it's also possible to do quite a bit to start with for a considerably smaller outlay of the hard-earned, especially if you are only doing it on a hobby basis. And if you have some mechanical experience, it's quite possible to take the MEW approach to tools, and build things like power supplies, basic function generators and counters for yourself. Multimeters that are good enough can be picked up for next to nothing in Maplin (and always impress SWMBO when you can use them for fuse checking, etc), and you can get scopes rather cheaper than £200 if you look around as well, although you have to exercise a little care here, admittedly.

 

With all of these things though, you have to recognise the limitations of them - and the limitations of what you're doing. Whereas you could buy a scope for £2000, the chances of you doing anything more than scratching the surface of its capabilities with your average PIC-based project are slender indeed. Yes, having a scope can be very useful - but we have to be a bit realistic about all of these toys, I think, because the trouble is, we tend to get greedy... do I need a Hardinge HLV-H? No, of course I don't, but I'd sure as hell like one!

Thank you Gentlemen, I've got a soldering iron and some little screwdrivers, thats a start heh? I remember when I was an apprentice fitter and turner, I was fortunate to operate a new NC Cinncinatti horizontal boring machine!! It was a huge thing, hydraulic pumps made a hell of a din, with a large cabinet with those old style reels with inch wide paper tape punched with little holes!!!!!!! It was space age equipment in those days, well it WAS 40 years ago. I remember the techs used an oscilloscope to fix her up when it went wrong, which was often. I asked what it did and they explained but I still don't have a clue. Had pretty little wavey lines on it right??? They used us apprentices because we were young and could learn quickly. Also we did as we were told, Tradesmen were gods!!!!!!!! Sorry, think I'm turning into an old fart!!

Regards

Dave

  

i found the uA723 to be a good low cost psu control ic. and for a few pounds you can easile build a 0-30V 0-3A power supply.

Having just completed Les's tacho I have to report that it works like a charm. The gear sensor datasheet describes its original purpose as the input for car ABS systems: certainly it works very nicely on a 65-tooth ml7 bullwheel. I just have to work out how to fix it in the correct position  (seems most happy at a radial separation of ~ 1.5mm).

Let's hope this very neat design appears in the magazine.

 

Hey Roy,
I've had electronics as a hobby since I was old enough to wield a soldering iron (about 10).
Books - better than the web, you can read them in the bath.
Two good books for starters are the Maplin Electronics Handbook by Michael Tooley and (for more detail, but costly) The Art of Electronics by Horowitz and Hill. But I learnt most of my stuff from reading datasheets - these days easily available from supplier websites. Sadly in  2010 there are fewer example circuits than there used to be in the 70's (the old 555 and 741 datasheets were an Alladin's cave of ideas).
 
Variable Power supply
I have NEVER had one of these until I made a simple one a year ago +/- 5 and 12V, plus 4-16 variable.
You can get REGULATED plug in power supplies that give a range of voltages, and a simple REGULATED 5V supply will do for most things, both quite cheap.

Multimeter
My main multimeter cost my dad about £60 - in the 70s, an Eagle, one of two he never used as he had an AVO. I still have it (and about six others), but I use a £10 digital one from Machine Mart 99% of the time (and its just as accurate and more precise).

Breadboard
Worth having, but a box of jump wires will cost rather more and is essential. You will rapidly get some veroboard and a soldering iron (18watt Antex or slightly bigger Weller - I prefer the former) if you want anything permanent.


Oscilloscope - worth having, if only for entertainment value
I got my 50MHz two-channel Hameg off Ebay for about £40 - keep bidding, but don't go too high. It took me two weeks but in the end I got what I wanted. Replaced a Heathkit one my Dad made in teh stone age.
Eseential if you want to tackle microprocessors.
I wont argue with MPLAB for PICs, but I use AVRs with Atmel AVR Studi 4.00a and WinAVR - also free (moral - look for the freebies!)
 
I have an STK500 development kit, this is not essential but something like that for AVR or Picstart(?) for PIC is a massive help.

nice to have
Function generator ~£100 - £1000
Frequency/period counter ~£150 - £1000.

I would consider making these; I have it isn't too hard to do once you get into the field, especailly if you use a custom chip and don't expect too much. But even the most basic will help you solve problems faster.

Schematic/PCB capture
Download Eagle demo version - the size of PCB is limited to about 3" by 4" and the learning curve is steep, but it's free for non-commercial use from their website. There is a link from the Farnell website (they bought Eagle).

It's a fascinating hobby and goes well with model engineering. They were very close in the 50s and 60s when RC fans made their models AND their radio gear!

Neil

 

Hi, I'm keen to add a tacho to my sieg x3. Has there been any updates to the circuit design recently?

 

thanks

alex 

Posted by Les Jones 1 on 16/01/2010 12:45:14:
Hi All,
            I have built tachometers for my lathe mill and drill press in the past. The design was governed  by an easy way to sense the rotation and what bits I had lying around at the time. I was wondering if there would be any interest in a tachometer that could cope with between 1 and 99 pulses per rev. If there was I do not know if it would be best to try to get the design published in "Model Engineers Workshop" (Where it would more likely interest readers.) or in "EPE" electronics magazine who are more set up to provide printed circuit boards and programmed PIC's   One pulse per rev is useful if there are no gears in the drive train. One pulse per rev can be sensed easily with a reflective marker and optical sensor. If there are gears in the drive train a hall effect gear tooth sensor is easy to use.  The display would be a four digit LED display reading from about 30 RPM to 9999 RPM
 
Regards
Les
(Ormskirk Lancs.)

 I'm a bit late chiming in on this thread, but I wrote an article for MEW - published in issues 115 and 116 - describing a PIC-based tachometer that I designed a while back & which is available in kit form from http://medw.co.uk/. The article describes sufficient detail to do a DIY version if so desired: see http://www.jeffree.co.uk/pages/revmaster.htm and http://www.jeffree.co.uk/pages/tachometer-pcbs.html

 

The design will accept a wide range of sensors, but requires the sensor to generate 1 pulse per rev, 6 PPR, or 60 PPR .

 

Regards,

Tony

thanks Tony, that's just what I was looking for

 

cheers

alex