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 Posted: Jul 31, 2012 - 06:04 PM |
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Joined: Feb 09, 2012
Posts: 223
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Hi,
Is there a H-Bridge driver ic with full-swing output at 12V that can do 40kHz ?
I want to make a dog/cat/bug/insect repellent with a 20kHz - 40kHz ultrasonic sound. I have 4 piezo tweeters of 4kHz-40kHz. An ATmega seems perfect for this, since I can vary the frequency, add a PIR motion detector, check the battery, and so on. The device will use a battery of 12V.
If I use a H-Bridge, the 12V should be enough, so I don't need a transformer.
The current would be about 40mA (20mA - 100mA).
I can make a short-safe H-bridge for 0.1V - 11.9V output, but I would need 8 transistors (BC547/BC557) per H-Bridge. So I hope there is an easier way. |
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Posted: Jul 31, 2012 - 06:40 PM |
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Joined: Nov 19, 2001
Posts: 918
Location: San Luis Obispo
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Why not a dual high-speed power mosfet driver?
The 4428 is a dual inverting & non-inverting driver with a stiff output. Rated to 18V and 1.5A, driving 1000pF in 25nsec…
Search Digi-Key or Mouser for 4428 Driver.
Stan |
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Posted: Jul 31, 2012 - 07:04 PM |
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Joined: Sep 04, 2002
Posts: 21272
Location: Orlando Florida
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| Or just a pair of logic mosfets. The piezos are capacitive in nature. Just store 01 then 10 in the two outputs at 40KHz (in the compare handler I suppose). |
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Imagecraft compiler user
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Posted: Jul 31, 2012 - 07:08 PM |
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Joined: Feb 09, 2012
Posts: 223
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bobgardner, I can easily use a whole port of a ATmega8 for the H-Bridge. So I can write 01 and 10 to the bridge, thanks. But just a pair of logic mosfets is that enough, the H-Bridge is at 12V.
Thanks sbennett, the MIC4428 is just what I need (logic input, very fast).
But I can't solder smd. Is there something like that as a DIL ?
.... searching Ebay ..... Ah, I think I found it. There are a number of dual mosfet drivers which I could use, like the TC428.
Thanks, I think I know enough. |
Last edited by Kun.io on Jul 31, 2012 - 07:25 PM; edited 1 time in total
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Posted: Jul 31, 2012 - 07:18 PM |
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Joined: Dec 29, 2007
Posts: 501
Location: Ontario, Canada
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Quote:
But I can't solder smd. Is there something like that as a DIL ?
According to the datasheet the MIC4428(CN), ZN, BN & YN are PDIP.
Additionally, you don't know you can solder SMD until you try. I find it easier and faster.. |
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Michael
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http://krazatchu.ca/
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Posted: Jul 31, 2012 - 07:28 PM |
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Joined: Feb 09, 2012
Posts: 223
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krazatchu wrote:
...
According to the datasheet the MIC4428(CN), ZN, BN & YN are PDIP.
Additionally, you don't know you can solder SMD until you try. I find it easier and faster..
I didn't read the datasheet very well then. Thanks.
And beleive me, I tried soldering smd. |
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Posted: Aug 18, 2012 - 04:30 PM |
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Joined: Feb 09, 2012
Posts: 223
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I used the UCC27424 which is also a bipolair/cmos combination, and this driver can do peaks of 4A.
The UCC27225 is invering/non-inverted, so I should have bought that one, but I added an inverter (HF transistor).
The problem is that is gets very hot with my piezo tweeter at 22kHz. After 15 seconds I can no longer hold my finger on it. If the temperature rises more there are ticks and cracks in the sound. |
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Posted: Aug 18, 2012 - 06:06 PM |
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Joined: Nov 19, 2001
Posts: 918
Location: San Luis Obispo
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Posted: Aug 18, 2012 - 06:27 PM |
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Joined: Oct 05, 2004
Posts: 133
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You can use an RS232 interface such as MAX232 which has a built in charge pump to drive a piezo with +-20V when powered from a 5V supply.
The MAX232 has two RS232 drivers, feed them with opposite polarity square signal and connect the transducer between the two outputs.
kevin |
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Posted: Aug 18, 2012 - 08:40 PM |
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Joined: Feb 09, 2012
Posts: 223
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sbennett, thanks for the links. Using 4 mosfet transistors for a full H-bridge would do, but I wanted something with less components and less soldering.
kevin_white, I don't think the MAX232 can do that. I need a lot of energy pumped into a piezo at 22kHz...25kHz for a dog repeller. I still found dog poo at 10 meters from my piezo peeper. |
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Posted: Aug 19, 2012 - 02:18 AM |
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Joined: Jul 02, 2005
Posts: 5949
Location: Melbourne, Australia
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... so you want your piezo pooper to be able to throw further than 10 metres  |
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Ross McKenzie
ValuSoft
Melbourne Australia
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Posted: Aug 19, 2012 - 07:21 AM |
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Joined: Feb 09, 2012
Posts: 223
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I read that the mosfet driver ic can be used parallel. So I solved it by soldering a second one on top (piggyback). I also sound the piezo for a short time, with pauses in between to let the driver ic cool down.
I'm going to make a second version with the same driver ic, but I used it to drive a H-bridge with 4 mosfets (that's what it is designed for anyway). |
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Posted: Aug 20, 2012 - 03:05 AM |
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Joined: Dec 30, 2004
Posts: 8788
Location: Melbourne,Australia
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| Silicon chip magazine had a similar thing published msny years ago that used a motorola piezo tweeter. See if you can get the circuit. |
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Posted: Aug 20, 2012 - 08:10 AM |
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Joined: Feb 09, 2012
Posts: 223
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Posted: Aug 20, 2012 - 10:16 PM |
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Joined: Dec 30, 2004
Posts: 8788
Location: Melbourne,Australia
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| Sounds like a tuned circuit. When you hit resonance, then the output will increase. |
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Posted: Aug 20, 2012 - 11:49 PM |
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Joined: Dec 29, 2007
Posts: 501
Location: Ontario, Canada
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If it were single ended, a current sense resistor feeding the ADC would be an easy way to locate your maximum power point...
Being in an H bridge will require differential unless you time your sense and protect your inputs.
Alternatively, measure phase angle and alter frequency to decrease the angle.
A brief example here: http://krazatchu.ca/2008/04/17/ultrason ... t-tracker/ |
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Michael
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http://krazatchu.ca/
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Posted: Aug 21, 2012 - 06:16 AM |
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Joined: Oct 31, 2009
Posts: 150
Location: Vancouver, WA, USA
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Why not try the NJR NJU8752 Class D Amplifier for Piezo Speaker. Link to Digi-Key.
Typical application shown in attached jpg. |
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Posted: Aug 21, 2012 - 08:04 AM |
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Joined: Feb 09, 2012
Posts: 223
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Thanks. This ic optimizes driving the piezo.
But I doubt if it is able to drive my 120dB ultrasonic piezo. |
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Posted: Aug 21, 2012 - 04:54 PM |
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Joined: Oct 30, 2002
Posts: 5720
Location: The Netherlands
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| How do you quantify whether it is or is not capable of driving your piezo? |
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Posted: Aug 21, 2012 - 05:14 PM |
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Joined: Dec 29, 2007
Posts: 501
Location: Ontario, Canada
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I wonder what the roll off is for the PAM8610..
I've a bunch of these and they don't get warm no matter what I try, even 15v supply and 4 ohm load.
http://cgi.ebay.ca/ws/eBayISAPI.dll?Vie ... 0952437309
The sound quality isn't top notch but what do you expect for $7.30
Somewhere it says not to bridge channels, I have not tried that yet... |
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Michael
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http://krazatchu.ca/
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