Retlas

[Alyn Foundry]

Very nice dynamos ...     Reminiscent of a Mather & Platt  I once knew.

Are they 3-brush? Can't quite see.

Dave

Hello Dave.

Ah Mather and Platt..... Brings back some fond memories. I started my working career with the Wrexham & East Denbighshire Water Company as an apprentice electrician.. One of my first experiences was replacing a bearing on the 450 HP motors that drove the massive Mather and Platt pumps.

The Retlas dynamo is commonly known as a " Manchester " style.

Kind regards, Graham.

[Alyn Foundry]

OK Graham I'll have to bring it up to show you when it has been painted and properly set up.
Mike C called in this afternoon to see the Retlas  running and to try out his Garretson demand valve on my engine - it ran just the same as with my home made valve. However, the Hall Effect sensor of my Minimag ignition system packed up, rather annoying as it has only lasted for about ten hours use. I was able to substitute a sensor from old RHC system that has different coloured wires but after some trial and error wiring set ups I got the engine running again.

I like the compact Minimag system but they charge £15 for a replacement Hall Effect Sensor kit, perhaps I was unlucky but I'm now looking for a cheaper source in case that happens again. The blown sensor is marked  451S OGL. As the Minimag system operates on two AA batteries I assume I need a sensor that is rated for a range starting at around 3V.

Looking on-line I see RS sell a Honeywell SS460S Sensor 'switching current 20 mA supply voltage 3 → 24 V dc' for £0.65
and another Honeywell SS49E-F 'current 1.5 mA supply voltage 2.7 → 6.5 V dc' for £2.48.

Can anybody interpret what make and model the defective sensor marked 451s OGL is and suggest a source (preferably UK) or advise me whether the choice of sensor is critical?

Thanks

Andy

Hi Andy.

Do you have a photo of the " offending " Hall effect transistor please ?

Kind regards, Graham.

[Chipmaster]

Hi Graham, here are four photos of the sensor which is 3mm square and 1mm thick, it is marked 451S  OGL.

P1060269 by Andy, on Flickr

P1060266 by Andy, on Flickr

P1060263 by Andy, on Flickr

P1060262 by Andy, on Flickr

Thanks
Andy

[Jasonb]

Might be worth contacting Julian at Minimag to see if he will supply just a new sensor rather than the wired up kit one

[Bluechip]

Andy

Maybe these are suitable. I've used them and they seem pretty robust. ( I can assassinate most semiconducters ...  )

http://cpc.farnell.com/allegro-microsystems/a1120eua-t/hall-effect-switch-unipolar-3sip/dp/SC10233

Cheap enough. ( If they work the same way as the one you have).

The o/p switches low with a south pole to the active face.

Dave

[Roger B]

Pavel (rarach22) had a fine homemade dynamo on his stationary steam plant. The photo links are broken, but I have PMd him to see if he can fix them.

[Chipmaster]

Hi Dave, thanks that looks good. The spec shown on the Allegro Microsystems website states,

"Hall Effect Sensor 25mA Unipolar 3.3V/5V/9V/12V/15V/18V 3-Pin Ultra Mini SIP Bulk" so I assume the voltage is ok. At that price its worth having a go. I don't know much about electronics, I know the sensor has to be set up against the correct pole. However you lose me when you say, "The o/p switches low with a south pole to the active face", I don't know how my blown sensor switched. I will have to experiment to find out which way to wire it up and point it towards the magnet.

Thank you very much for your help Dave

Andy

[Chipmaster]

Hi Jason, I'll try approaching Minimag if I can't find a cheaper solution at least I can keep running the engine using the sensor from the RHC ignition kit.

Andy

[Chipmaster]

Hi Roger, that would be interesting to see.

Andy

[Bluechip]

However you lose me when you say, "The o/p switches low with a south pole to the active face", I don't know how my blown sensor switched.

Not much to it. If you run the device from (say) 12V, the output pin will be at, or very near, 12V with no south pole magnetic field near it.

When such a field of sufficient intensity is applied it will pass current through the load resistor causing the bottom end of it ( the o/p pin ) to approach 0V, or close.

http://www.farnell.com/datasheets/1804644.pdf

Look at P12. ( diag. C )

And while we're getting all geeky about it, where's the bypass capacitor from the supply to ground? Should be close to the device. Bit of an iffy design to leave it off.   

That's on P12 also, See 'woe-betide'  note re: same .

They do have the effect, amongst others, of helping protecting the device from voltage spikes.

Dave

Obligatory Dietary Note

No pancake for me. Black Pudding instead ... 

Nighty-night

[Chipmaster]

Good morning Dave,
I have no knowledge of electronics so I can't go geeky with you. Don't know whether a pair of AA batteries can produce voltage spikes, perhaps there is a bypass capacitor inside the Minimag black box?

I will follow up your suggestion and order a few sensors from CPC today.

Thanks
Andy

[Bluechip]

Graham:

Batteries won't produce spikes in themselves. The spark current can.

Are we looking at one of these ??

http://minimagneto.co.uk/documents/MCL-1.pdf

I can find no sensible reference searching for the MHS-LV ??

Does not look like any sort of device ID to me ... 

That CPC item should work @ 3V anyway.

I will continue when I've done scraping the bituminous paint off me paws ... knew I should have used gloves ... 

Dave

[Alyn Foundry]

Graham:

Batteries won't produce spikes in themselves. The spark current can.

Are we looking at one of these ??

http://minimagneto.co.uk/documents/MCL-1.pdf

I can find no sensible reference searching for the MHS-LV ??

Does not look like any sort of device ID to me ... 

That CPC item should work @ 3V anyway.

I will continue when I've done scraping the bituminous paint off me paws ... knew I should have used gloves ... 

Dave

Hello Dave.

I think you might have had " one too many black puddings lad " ......

Andy was asking about spikes.

Kind regards, Graham.

[Bluechip]

Oops! Sorry ....   

Nowt to do wi' Black Puddings .... Just general mental decay ... 

Dave

[Chipmaster]

Hello Dave,
Yes we are looking at one of these http://minimagneto.co.uk/documents/MCL-1.pdf.

Could you tell me what the insulating sleeves are likely to be on my sensor so I can order some and should I use some sort of heat sink when I solder the three wires onto the sensor? I am concerned heat shrinking insulation might destroy the sensor.

Andy