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Author Topic: Peterborough timer  (Read 8710 times)
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Daithi
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« Reply #75 on: January 10, 2012, 09:12:08 PM »

Full how to with diagrams here (Peterborough MFC website Wink )

http://www.peterboroughmfc.org/technical-articles/web_site_FETtimer.pdf
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mike_st
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« Reply #76 on: January 11, 2012, 03:45:37 AM »

I think things are getting confused because 2 different pdfs are being referenced.
I've ordered some std12nf06lt4 and will try those next.
- Mike
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Daithi
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« Reply #77 on: January 11, 2012, 04:27:40 AM »

Well I supposed being a 'Peterborough' timer that the guys at Peterborough would be the best source Wink  Grin  Cheesy
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slipstick
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« Reply #78 on: January 11, 2012, 04:35:01 AM »

Full how to with diagrams here (Peterborough MFC website Wink )

http://www.peterboroughmfc.org/technical-articles/web_site_FETtimer.pdf
Ah now it's easy to see where all the confusion comes from...the pins in that article are marked incorrectly and that makes the text wrong. The "D" is actually against the Source pin and the "S" marks the Drain pin. The picture is basically correct but when you build it so it LOOKS like the picture the capacitor and resistor are across Gate and SOURCE not Gate and Drain. To get an N-channel FET to switch on (i.e. connect Drain to Source) you need a +ve voltage on the GATE with respect to the SOURCE.

A quick Google of the datasheet for any of the referenced FETs will soon tell you which pin is actually which.

Steve
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Woodster
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« Reply #79 on: January 11, 2012, 05:29:23 AM »

Yeah, this looks different to the Peterborough PDF:

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00002633.pdf

 Huh
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Dave Andreski
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« Reply #80 on: January 11, 2012, 10:18:15 AM »

Full how to with diagrams here (Peterborough MFC website Wink )

http://www.peterboroughmfc.org/technical-articles/web_site_FETtimer.pdf
Ah now it's easy to see where all the confusion comes from...the pins in that article are marked incorrectly and that makes the text wrong. The "D" is actually against the Source pin and the "S" marks the Drain pin. The picture is basically correct but when you build it so it LOOKS like the picture the capacitor and resistor are across Gate and SOURCE not Gate and Drain. To get an N-channel FET to switch on (i.e. connect Drain to Source) you need a +ve voltage on the GATE with respect to the SOURCE.

A quick Google of the datasheet for any of the referenced FETs will soon tell you which pin is actually which.

Steve

Steve,
GOOD EYE! That is quite a blatant error. I think this solves Mike's problems.
When I started making these I paid NO attention to how things were labeled and simply wired things up according to the 'look' of the completed device paying attention to capacitor polarity.
Ignorance is bliss!
Dave Andreski
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Dave Andreski
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« Reply #81 on: January 11, 2012, 10:54:17 AM »

It says in the PDF: Solder the capacitor and resistor to the (G) and (D) pins of the FET. It then says solder a red wire to the (S) pin on the back of the FET and a black wire to the (D) pin. There is then a small diagram showing how to wire it up to the motor/battery. The only slightly unclear part (for me!) are the "Zapper" connections - I'm assuming +9V to (G) and -9V to (D).
Woodster,
Thanks to Steve (slipstick) we now know that the diagram is incorrect.
When the timer is wired correctly the 'Zapper' or 9 volt battery should make contact on the resistor wires/whiskers following the polarity of the capacitor.

Dave Andreski
« Last Edit: January 11, 2012, 11:19:55 AM by Dave Andreski » Logged

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Woodster
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« Reply #82 on: January 11, 2012, 01:40:06 PM »

Thanks Dave. After it was mentioned that there were earlier "instructions" I searched out this:

http://www.peterboroughmfc.org/newsletters/2005-01.pdf

And photo 4, at the top of page 5 seems to cover it!
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Woodster
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« Reply #83 on: January 16, 2012, 08:59:47 AM »

How's it going Mike, did you get it working?
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mike_st
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« Reply #84 on: January 16, 2012, 02:26:46 PM »

How's it going Mike, did you get it working?
not really! with a 1000uF capacitor and a 10meg resistor and a buz71a I can get about 5 seconds  Huh We'll see  whether I have more luck with the std12nf06lt4 when it arrives.
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slipstick
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« Reply #85 on: January 16, 2012, 03:35:51 PM »

Something very odd going on. Just for interest what voltage are you running the motor on ?

Steve
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Daithi
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« Reply #86 on: January 16, 2012, 06:49:56 PM »

The time constant on that is seriously out of whack - theoretically that should be a 2 1/2 HOUR duration (10,000 seconds).

Did you check for hairline shorts on the soldering? It's the easiest thing in the world to do (trust me - I've done it before now and it's hair-tearing time trying to FIND the short, especially when it's that small)
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mike_st
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« Reply #87 on: January 16, 2012, 10:20:49 PM »

Something very odd going on. Just for interest what voltage are you running the motor on ?

Steve
kp00 with 1x 50mah nicad, which peaks at about 1.7 v and settles down to 1.3v. Though I tried a small lipo as well.

Did you check for hairline shorts on the soldering? It's the easiest thing in the world to do (trust me - I've done it before now and it's hair-tearing time trying to FIND the short, especially when it's that small)
well I've tried 3 different buz71a's with a variety of caps and resistors, so I dunno how I've replicated the same problem each time!
I'll keep fiddling.
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Woodster
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« Reply #88 on: January 17, 2012, 04:48:14 AM »

I believe it was designed to run on a 1S LiPo so that may have a bearing on it?
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boffin99
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« Reply #89 on: January 17, 2012, 03:34:48 PM »

Slipstick : Thanks for finding my error in the Technical Articles file. These have now been corrected. Build the timer to these notes and you cannot fail.

http://www.peterboroughmfc.org/technical-articles/web_site_FETtimer.htm

Woodster: Is does not matter what battery you are using. Applying a voltage to the gate, makes the FET conduct.

Mike_st : The surface mount FET is not the answer. If you cannot get BUZ 71 going then the surface mount FET will also disappoint.

I think you have suffered enough. PM me for my address and send me your best effort. I will sort it out and return something functioning correctly. In fact tell me what max duration you are after and I will see that you get it. Absolutely no charge, the reputation of the Peterborough MFC is at stake !

Regards Ian

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Dave Andreski
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« Reply #90 on: January 17, 2012, 05:45:36 PM »

That's a very kind offer IAN. I hope Mike takes advantage of it.
Dave Andreski
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mike_st
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« Reply #91 on: January 18, 2012, 03:22:25 AM »

That's a very kind offer IAN. I hope Mike takes advantage of it.
Dave Andreski
It certainly is  Cheesy
But I have not exhausted my stubborness yet. It is of course an affront to my very minor intelligence that I can't get it working  Grin This is where I go "but I've built all manner of DIY electronics for years. I can build solid state and valve guitar amps! microphone preamps! audio compressors! guitar effects pedals! battery chargers! hot wire cutters! power supplies! I'm not going to let 3 components get the better of me!" But maybe I'll take some of the troubleshooting offline with Ian until I can report success.
Cheers
Mike
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Woodster
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« Reply #92 on: January 18, 2012, 05:26:44 AM »

I really hope you get it working Mike, and let us know when you do  Smiley
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mike_st
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« Reply #93 on: January 19, 2012, 02:55:48 AM »

got it working - how's this for a do'h.....in my test rig I connected the zapper to G&S with alligator clips, and used the push button to initiate a run. Because the zapper was still connected, G&S were effectively permanently shorted by the zapper pot, so no or very little resistence to stop the cap draining, hence no useful run. By taking away the alligator clips, off it went as designed!

I did mention my very minor intelligence  Shocked

Thanks to all who helped! Now into a model it will go.
- Mike
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« Reply #94 on: January 19, 2012, 04:14:58 AM »

Well done Mike!  Smiley Lets see some pictures of it if you get a minute.
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slipstick
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« Reply #95 on: January 19, 2012, 04:21:33 AM »

Congratulations....and I should really apologise because I even thought about "leaving the zapper connected" but it seemed almost insulting to ask. Ah well, I've missed a good few "obvious" things in my time too Wink.

It's all really easy after this....just building and flying Smiley.

Steve
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Dave Andreski
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« Reply #96 on: January 19, 2012, 10:02:55 AM »

Mike,
Good for you! Another one of those 'head slapping' moments huh?
Dave Andreski
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ferfecir
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« Reply #97 on: April 18, 2012, 03:18:22 AM »



hello
 I want to make 504 euros Pistachio scale
 I want to make here is the timer.
 Do not have all the material in Turkey: (
 I found these parts. Does it works with these timers?

 Part Connections will be like in the picture?

http://www.dorukanstore.com/470K-1-Metal-Film-Direnc-50Ad-Fiyati,PR-14390.html
http://www.dorukanstore.com/33uF-16V-C-Kilif-SMD-Tantal-RoHS,PR-9249.html
http://www.dorukanstore.com/MTP3055E,PR-1592.html
http://www.dorukanstore.com/36V-60mAH-Ni-Cd-Sarjli-Hafiza-Pili,PR-12708.html

Attached files Thumbnail(s):
Re: Peterborough timer
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boffin99
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« Reply #98 on: April 19, 2012, 01:25:15 PM »

The above parts will be OK to make a Peterborough FET timer.
Also the hook up diagram is fine.

I hope you will post the results of this venture?

Ian Peterborough MFC
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Dave Andreski
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« Reply #99 on: April 24, 2012, 01:06:47 PM »

Sorry I missed this post.
I must say that the battery chosen, if for a Pistachio or similar sized Model, is far too heavy.
Dave Andreski
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