Member postings for Peter Bell

All interesting stuff.

I find I quite like using my Avo 8 occasionally especially if I'm reading current, I find it far easier to follow a swaying needle rather than rolling digits and of course it doesnt power off after a few minutes.

Peter G4LSA

Yes spring loaded shrouds were really annoying with leads popping off all the time. Also had bad experiences with lower priced meters belonging to others, the meters work fine but the leads just dont last.

Sorted for now but its opened my eyes to whats available for the future so thanks everyone.

Peter

Yes looks like they are GPO/BT and we all want some!

Think I bought a box of them at the Telford rally some time ago. Cannot find the box which would have the part no on them.

Peter

I'm running short of simple meter probes, eveything I look at is either expensive rubbish or not what I want.

This is what I've previously used, plugs onto a bannana plug lead (4mm?) so I can change it for a croc clip.

Does anyone recogise them and know if anything similar is still available?

Thanks Peter

Looks an interesting project. I've found it useful to listen to interference like this with a radio off station especially on am. You can also gauge where its from and intensity which may help with siting the application.

Recently found an Arduino nano was being reset when I switched my soldering iron off which contains a conventional transformer for the psu. I could hear the click on my fm radio, addng a supressor to the transformer cured the click and the nano doesnt reset.

Peter

Dave, Thanks.

Yes a 16x2 lcd will be fine, once its showing on the serial monitor I can manage. Arduino seem good on displays and I found I2C works well. Its just that the TFT displays are so cheap I bought one!

Peter

LOts of slave dials around and I would certainly be interested in seeing an Arduino use an RTC (I have a ZS-042) to generate 30 sec pulses for a slave and if possible display the time on a 1.8TFT display (I have a ST7735B)

I am probably ok with the electronics but perhaps SOD could do a mini series like he did for the CAD?

Seems so sad to see these slaves "quartzed" and lost for ever!

Thanks Peter

This generator is powered by a National engine at the Anson Museum.

The generator which is French appears to be in good condition but the board wiring has suffered some corrosion, also its been changed around a bit somewhere in its life. The exciter is close couples to a 13kw ac generator with a reostat to control the exiter field current to control the generator field. The generator is single phase with 2 slip rings.

Can anyone help by identifying the maker from the plates in the pics? A diagram would be ideal but I realise this is a really long shot!

Peter

Thanks for the suggestions.

A screw through the centre with a washer under a nut just about did it but tended to deform the coils slightly but points towards the coils need restraining while the end is bent.

I have tried clamping the spring to the mandrel after winding but it all tends to come apart as the wire end is bent. Also tried with ready made springs but the dimentions are critical as the sprung shaft is inserted into a hollow shaft when it is working.

Tried more searching on the interweb and found this video of a machine doing what I want. It looks like a plate bored to suit the spring clamps the spring to the base then the end is bent. Never added a vid before, hope it works!

Thanks for the reply.

Should have mentioned that I've tried various types of pliers without success as it tends to deform the end coil and you cannot get the sharp bend needed. to fit into the slot.

I want to make a 6mm od torsion spring using 1mm wire. I can wind a spring fairly well on the lathe after following various instructions online but I am having problems forming the end so that they are inline with the spring and are 180 degrees apart.

The spring fits onto a shaft and the ends go into slots. The left end is fixed and the arm is spring loaded, its part of a printing numbering box. I can form the first end before winding but forming the other end neatly after winding has defeated me so far.

I think I need some sort of jig to accuratly forn the ends but hope some with more experience can offer guidance on its construction?

Peter

Canned pies may be rubbish but the tins are really ace for putting nuts and bolts in when you dismantle anything!

Peter

Id previously came across someone else who had problems with low resolution printer tape while trying to use it for a linear scale so left that one alone. I also recently came across an ic which read magnetic tape but decided that would need a quite a lot of development to make it into a working linear encoder?

The common ebay Chinese rotary encoders appear quite well made and seem to come in a few different specs with pulse per revs ranging from 360, 400 and 600 with a great lack of manufactures info in the traditional manner. However some listing have snippets of info, like

Pulses: 600 p/r (Single-phase 600 pulses /R,Two phase 4 frequency doubling to 2400 pulses)

Output :AB 2phase output rectangular orthogonal pulse circuit, the output for the NPN open collector output type

So it looks like a 600ppr one is capable of 2400 pulses/rev quad? Assuming that, from a quick stab at a calc I make the drum dia around 0.75” to give 1 thou resolution with 0.5mm stainless wire? I’m sure someone will correct me but it seems a starting point to try when the encoder arrives and I can rig something up to try it on the mill with the leadscrew sensor as a standard as suggested.

Also the outputs appear to use open collector npn transistors which need a load resistor (1k etc to +5v) to give out the correct waveform?

Agree a draw wire sensor not ideal but its not terribly expensive to give it a bash and I used the BW electronics one successfully for years.

Peter

Hi Bob & Duncan,

Thanks for the helpful replies and Duncan with your work in getting the original DRO up and running for all to use. I’m not very experienced with Arduino but working on it! The LCD displays are good but I was wondering if a 7 segment display with be better and less critical of the viewing angle. Got a Max7219 8 digit 7 segment module on order to play with.

I had thought of a retractable key ring but realised that I have a few scrap 3m tapes. Dismantled, this revealed a 0.12 thick, 9mm wide return spring easily long enough to try. This I was going to put in a spring barrel at one end. Have two plates with the wire drum in the middle and the encoder at the other end on a ball bearing spindle if you see what I mean.

Yes that was the encoder I was going to use. It hasn’t arrived yet but I also found this magnetic type which gives a genuine 256 ppr. Could do with a higher count but want to avoid gearing. The wire drum dia is something unknown at present but the BW Electronics version looks to be fairly coarse on the encoder and uses a drum about 0.8” dia. Any guidance on drum dia will be gratefully received!

Peter

https://uk.rs-online.com/web/p/rotary-encoders/7140237/

I have had success with a dro based on a rotary encoder fitted to the lead screw of my mill described on the site below.

Home Brew DRO – WDMES - Warrington & District Model Engineering Society

I have another DRO application but this time I would like to make a draw wire spring return linear encoder but using a rotary encoder in the style of one in the pics from BW Electronics which works well.

I know there are commercial units units available at suitable prices but before attempting I wondered if anyone had constructed one using an optical (ebay around £8.00) or magnetic rotary encoder?

Peter

Thanks all for the input and detailed understandable explanations on "spin" and the advantages of interrupt, points taken. Dont really like asking so much but cannot think of any other way!

It's been suggested that one way of dealing with switch bounce if using interrupt is to add detachinterrupt to the code but there must be a catch as its never been mentioned?

Only previous programming experience is with picaxe but that has an excellent simulator to help which I miss but its all good experience especially with the vast amounts of Arduino info out there.

Peter

A friend had a a similar problem, ie nothing wrong and new lights and it turned out the electronic ballasts were voltage sensitive and the incoming supply was occasionally too high causing them to shut down at random. He cures it by switching a water heater on when it happens.

Thanks Neil, I'll have to work on that one once I get my head around the present learning!

Peter

Hi Dave,

Thanks for all that, your description on debounce sounds logical. Yes a 100nf almost fixes it, adding a 1k resistor in series completely cures it as far as I can see. I'll have a look at the bounce libraries, a quick search reveals a lot to choose from.

Thanks also for the spin, makes sense apart from the syntax I'm afraid. The curly brackets with the semicolon inside are used to end a statement according the reference? { ; } I'm sure there's a simple explanation!

// Spin waiting for input

while ( digitalRead( switch1 ) == HIGH ) {
// Do nothing
;
}

Also adding a LOW digital read version first stops it just rolling through so that it increments each complete input cycle, what is the advantage of interrupt which (to me!) appears to be doing the same job?

Peter

Hi Dave,

I must admit I thought that cut and past was just that, never realised what the editor was doing by tangling things around like that, another lesson learned.

The drop version works perfectly once I restored my lcd so many thanks for your help, still untangling what its all doing but its great to be learning and making progress at the same time. The switch bounce is horrendous but at least the serial numbers agrees with the lcd. The software solutions look very involved in the versions found so far so I'll try adding some r&c to see that the effect is. It may be ok in real life as I'm using a proximity sensor but I dont know what the rise time is yet.

You mentioned earlier "spin digitalRead() in a loop until a pulse is detected, then count it." as an alternative to attachinterrupt, could you point me to some info on it? Thanks

Peter