Weird piezo driver
http://imgur.com/Trvs5mk
This is a beeper piezo in a Fluke 117 DMM which quite beeping. Scoped the piezos pads and... nothing. An inverter (from the CD4069) is connected across the piezo. Guess I dont understand anything about driving piezos. Is this a standard practice? Cheers. |
Weird piezo driver
On 16/05/2016 07:36, DaveC wrote:
http://imgur.com/Trvs5mk This is a beeper piezo in a Fluke 117 DMM which quite beeping. Scoped the piezos pads and... nothing. An inverter (from the CD4069) is connected across the piezo. Guess I dont understand anything about driving piezos. Is this a standard practice? Cheers. My Fluke 77, will beep when the battery is low but not low enough to trigger the LCD legend, presumably drift over time |
Weird piezo driver
On 16/05/16 16:36, DaveC wrote:
This is a beeper piezo in a Fluke 117 DMM which quite beeping. Scoped the piezos pads and... nothing. Did you mean that "it quit beeping"? If so, you aren't going to hear anything. An inverter (from the CD4069) is connected across the piezo. Guess I dont understand anything about driving piezos. The Fluke should be producing a square wave, say 1KHz, across the piezo. The piezo itself looks like a mid-sized capacitor; you won't get any DC resistance reading through it. They are extremely high resistance devices. If you touch 9v to either side of the piezo, you should hear it click, and click again when you disconnect. The Fluke does that too, but fast. |
Weird piezo driver
On 16.5.16 09:36, DaveC wrote:
http://imgur.com/Trvs5mk This is a beeper piezo in a Fluke 117 DMM which quite beeping. Scoped the piezos pads and... nothing. An inverter (from the CD4069) is connected across the piezo. Guess I dont understand anything about driving piezos. Is this a standard practice? Cheers. You'll get AC drive when you drive one side with a logic signal and the other side with the same signal inverted. -- -TV |
Weird piezo driver
On Sun, 15 May 2016 23:36:38 -0700, the renowned DaveC
wrote: http://imgur.com/Trvs5mk This is a beeper piezo in a Fluke 117 DMM which quite beeping. Scoped the piezo’s pads and... nothing. An inverter (from the CD4069) is connected across the piezo. Guess I don’t understand anything about driving piezos. Is this a standard practice? Cheers. If you put an inverter across the piezo you get double the supply voltage drive - push-pull. Not uncommon. Typically you'd drive each side with two paralleled inverters and use another inverter to invert the input to one pair. The piezo element looks something like a ceramic capacitor electrically. A series capacitor is often used. --sp -- Best regards, Spehro Pefhany Amazon link for AoE 3rd Edition: http://tinyurl.com/ntrpwu8 |
Weird piezo driver
On 16 May 2016, Clifford Heath wrote
Did you mean that "it quit beeping"? Yes, €śquit€ť beeping. Thanks. |
Weird piezo driver
In article
, DaveC wrote: http://imgur.com/Trvs5mk This is a beeper piezo in a Fluke 117 DMM which quite beeping. Scoped the piezos pads and... nothing. An inverter (from the CD4069) is connected across the piezo. Guess I dont understand anything about driving piezos. Is this a standard practice? Cheers. Piezo drivers have a high impedance so they need high voltages. One side of that piezo element is driven with the signal source and the other side is driven with the inverted signal. That doubles the drive voltage so it's loud enough to hear. -- I will not see posts from astraweb, theremailer, dizum, or google because they host Usenet flooders. |
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