Specialist Posted October 15, 2010 Share Posted October 15, 2010 Piezo's need ac just like speakers. So no i dont currently think i have. Sorry James, but you have. Piezo sounders work on DC. Customers Love us, Intruders Hate us. Link to comment Share on other sites More sharing options...
james.wilson Posted October 15, 2010 Share Posted October 15, 2010 I dont mean the whole sounder, i mean the piezo parts (ie the speaker like parts) You apply apply dc to them then they wont occilate and as such wont make any noise. securitywarehouse Security Supplies from Security Warehouse Trade Members please contact us for your TSI vetted trade discount. Link to comment Share on other sites More sharing options...
MrHappy Posted October 15, 2010 Share Posted October 15, 2010 can't say I've ever bothered to check but assume a piezo need AC to vibrate, old sab made from bits (or regalsafe ones) have speakers with a platic cones, same as a driven internal ones Mr Veritas God Link to comment Share on other sites More sharing options...
Guest Oxo Posted October 15, 2010 Share Posted October 15, 2010 A little snippet A piezo sounder is a piece of crystal which changes shape (moves) when you apply a voltage across it No AC is required. Sorry to use this link but, http://www.securitywarehouse.co.uk/catalog/index.php?main_page=product_info&products_id=1183 Link to comment Share on other sites More sharing options...
james.wilson Posted October 15, 2010 Share Posted October 15, 2010 Yes but there is a driver board in that unit so its a 12v input. But the actually piezos like all piezos run ac. Its like saying car speakers run on dc cos the head unit runs 12v dc securitywarehouse Security Supplies from Security Warehouse Trade Members please contact us for your TSI vetted trade discount. Link to comment Share on other sites More sharing options...
Guest Oxo Posted October 15, 2010 Share Posted October 15, 2010 I`ll rephrase, some do work on DC only. Link to comment Share on other sites More sharing options...
arfur mo Posted October 15, 2010 Share Posted October 15, 2010 Yes but there is a driver board in that unit so its a 12v input. But the actually piezos like all piezos run ac. Its like saying car speakers run on dc cos the head unit runs 12v dc you are right James, the pietzo that makes a noise needs via a driver (for refference you can buy with or without a driver pcb versions from maplins and RS), so some have a pcb built in like a sound bomb other designs have the driver circuit on a pcb externally (thik old flash guards guys) the pietzo elements usually works on high frequecly signals generated by the driver boards, designed to handle the power i'm guessing this siren has 2 pietzo's eleiment outputs where each pietzo is on a different ramping square wave cycle (which might be chopped dc), both wired to a common for convenience. Arfur If you think education is difficult, try being stupid!!!! Link to comment Share on other sites More sharing options...
james.wilson Posted October 15, 2010 Share Posted October 15, 2010 Yes i noticed the component specs talking about peak to peak voltage. Id assume 20v + would move it to one position, 0v back to rest and 20v - the other way. Obviosly the element would have to move as quickly as possible between its 2 maxed positions. I have no idea what voltage the elements themselves run at mind and assume its pretty high to achieve the pressure they do. securitywarehouse Security Supplies from Security Warehouse Trade Members please contact us for your TSI vetted trade discount. Link to comment Share on other sites More sharing options...
Guest Oxo Posted October 15, 2010 Share Posted October 15, 2010 5v square iirc,as I said not all need AC. I`ll go abck to banging head on wall, far easier. Correct and hurts less. Cannot be bothered to correct spelling. Link to comment Share on other sites More sharing options...
hpotter Posted October 15, 2010 Share Posted October 15, 2010 two thin crystal discs with diapham in middle (diaphram makes the noise). introduce electric charge to 1st crystal & it expands, bending diaphram. introduce charge to 2nd & that expands but will only bend diaphram other way if charge on 1st is removed. effecively applying & removing dc to both discs in an alternating way. LOL, hope thats clear. (thats what the driver does - as arf mentioned) Link to comment Share on other sites More sharing options...
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