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Help! - Parking Radar problems

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2005-2006 » Archive through 11 November, 2005 » Help! - Parking Radar problems « Previous Next »

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Glynshaw
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Username: Glynshaw

Post Number: 4
Registered: 06-2005

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Posted on Friday, 04 November, 2005 - 05:53 pm:   Edit Post Delete Post Print Post

I have built the Back to Basics parking radar (EPE October 2005) on breadboard, using sealed transducers. Despite adjusting the transmit frequency (using VR1) and changing R8 to change the logic high threshold of IC2a, I can only get a range of about 25cm at best. Has anyone experience of using sealed ultrasonic units? Are they less sensitive that the open types? I have PDF files of the transducer data sheets but I don't have the knowledge of amplifier design to modify the circuit. Any info/suggestions greatly appreciated.
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Harris584
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Username: Harris584

Post Number: 8
Registered: 05-2005

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Posted on Saturday, 05 November, 2005 - 11:50 am:   Edit Post Delete Post Print Post

I have used the sealed type and found them much less sensitive than the unsealed type. In fact I was unable to get them to work at all satisfactorily. Unfortunately, the sealed type would be ideal for the car as they prevent the ingress of water.
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Cherrytree
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Username: Cherrytree

Post Number: 72
Registered: 08-2005

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Posted on Saturday, 05 November, 2005 - 11:53 pm:   Edit Post Delete Post Print Post

}
Hi Glynshaw,
re your problem with sealed transducers YES they are no good in my opinion,
use the 40khz open type, as regarding amplifying the output try I say try the LM386 amp that give a 200db gain, you have to just add something like a resistor to the LM386.. or its sort of set by 20 db.. Im

Not up on this completely but read it enough!! or for very high power output use a TDA2030 amp IC 14Watts .. in a single chip..
if all that fails get the whole system including transducers ready done by Maplins
ok code LO3AC

hope this helps..
the ultrasonic transducers are NOT easy to operate but I got one working once, just as a ultrasonic transmitter running at 40khz. you use a trimmer pot to get the precise frequency
ok?
CT
let me know how you get on it sounds an interesting subject
CT
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Glynshaw
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Username: Glynshaw

Post Number: 5
Registered: 06-2005

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Posted on Monday, 07 November, 2005 - 10:47 am:   Edit Post Delete Post Print Post

Thanks everyone. I'm glad I'm not the only one who has found sealed units hard to work with! A while ago I built a Vellemann car radar kit which uses open types & it worked OK for about a year - I think the water destroyed it in the end. I'll keep trying with the sealed types - I haven't tried using an LM386 amp but I have tried various op amps. In the meantime I followed Cherrytree's suggestion - on Saturday I bought the Maplin built unit which uses sealed transducers!
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Cherrytree
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Username: Cherrytree

Post Number: 81
Registered: 08-2005

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Posted on Tuesday, 08 November, 2005 - 05:29 am:   Edit Post Delete Post Print Post

}
Hey Glynshaw,
your joking eh? sealed type in the maplin kit??
well thats weird because in my maplins catalog
it shows two transducers housed in a neat bit of black sleeving as if there in a tube style design

Are the ones you bought covered by that very fine wire mesh?
let me know on that.. because if there sealed & you want unsealed then drop me a line for a link
Oatley.com do open types
dunno if they in the uk.. Are U in the UK?
just to let you know and all elese I am
cheers
CT

Ps :sorry glynshaw.. if Id know they were sealed type I would not of suggested that unit/kit opps
CT
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Glynshaw
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Username: Glynshaw

Post Number: 6
Registered: 06-2005

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Posted on Wednesday, 09 November, 2005 - 11:19 am:   Edit Post Delete Post Print Post

Hi Cherrytree!
No problem - the unit I bought at Maplin wasn't a kit - it was a ready-built "car radar" unit (called the JML Parking Sensor) made by a company called John Mills Ltd. I can't find it on the Maplin website - I bought it in a Maplin store in London. I've given it a quick test and it seems fine. Its sensors are sealed and made of black plastic. It's interesting that this company have found a way of making the sealed ones work!

The sealed sensors I had trouble making a circuit with are shiny metal and I got them at Rapid. I will try again with them but I'm not optimistic!

Thanks for your advice by the way.

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