RE: Battery Safety
Scott, Thanks for the nice answer. Barry Ma - On Tue, 26 September 2000, Scott Lacey wrote: Barry, These use magnetic coupling to transfer the charging energy. In essence, the transformer secondary is inside the toothbrush handle, along with the rectifiers and rechargeable batteries. The older models used line-frequency sine waves and tended to get warm (but not hot). Many of the newer models use high-frequency (tens of kilohertz or higher) square waves and do not get warm while in the stand. As for safety, the lack of exposed contacts is a great advantage. Battery chargers can deliver substantial current - enough to cause burns to a curious child probing them with a pair of metal tweezers. Scott Lacey ___ Free Unlimited Internet Access! Try it now! http://www.zdnet.com/downloads/altavista/index.html ___ --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Battery Safety
Hi Barry, One of my clients makes a charger with primary loop in the base and the charged unit has a secondary loop to form a transformer, though less efficient than close-coupled versions there are no contacts to corrode or offer the possibility of shock . Mike Harris/Teccom -Original Message- From: Barry Ma barry...@altavista.com To: emc-p...@majordomo.ieee.org emc-p...@majordomo.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: Monday, September 25, 2000 6:18 PM Subject: Re: Battery Safety Chris' email reminds me of a relevant question: The charging stand for a battery-driven toothbrush (Sonicare) has no contact with the toothbrush. What is the charging mechanism? Is it safer than other battery? Best Regards, Barry Ma ___ Free Unlimited Internet Access! Try it now! http://www.zdnet.com/downloads/altavista/index.html ___ --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Battery Safety
Chris' email reminds me of a relevant question: The charging stand for a battery-driven toothbrush (Sonicare) has no contact with the toothbrush. What is the charging mechanism? Is it safer than other battery? Best Regards, Barry Ma ___ Free Unlimited Internet Access! Try it now! http://www.zdnet.com/downloads/altavista/index.html ___ --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Battery Safety
I've seen this resistor used for the low battery alarm circuit. It keeps the battery voltage from rising as load is shed and confusing the low battery alarm circuit. There is no safety reason that I know of. 91K ohm is an odd value though, left overs from another product? I'm assuming that the normal current drain of this product is small, in the 10 to 100 microamp regions. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
RE: Battery Safety
Hi, I've seen this done before on low current designs. Sometimes when you replace the batteries in this type of design the circuit voltage does not have time to drop completely away due to the charge saved on bulk capacitors. When the new batteries are added the circuit comes up in a peculiar state. This is particularly true of uP power on reset circuits. There are more elegant ways to take care of this problem but I suppose a single resistor would be the cheapest (if one ignored battery life). Regards, Kevin Harris Manager, Approval Services Digital Security Controls -Original Message- From: Maxwell, Chris [mailto:chr...@gnlp.com] Sent: Monday, September 25, 2000 11:31 AM To: 'EMC-PSTC Internet Forum' Subject: Battery Safety All, We have inherited a design from a company which we purchased. The product is a handheld and can be operated from a pair of Alkaline batteries. Inside the unit, there is a 91 KOhm resistor across the + and - terminals of the batteries. Since the people who designed the instrument are long gone, some of my collegues have asked me if this resistor could be a safety feature. I can't think of any way this resistor would help the safety of the instrument. I did read through the safety test report; and I found no reference to this resistor being required. All it does is provide a constant drain on the battery (reducing battery life). It has been suggested to me that some designers put resistors across batteries to reduce the electrical noise in a product. To me a capacitor would be better for this because it wouldn't drain the battery while it was filtering. Even so, isn't a battery the ultimate capacitor? I'm just drawing a blank why anyone would do this. I'd love to recommend that we pull this resistor out because it's a pain to solder and it affects battery life. However, I don't want to sacrifice the safety of the product. Anybody want to take a guess at this one? Thanks. Chris Maxwell, Design Engineer GN Nettest Optical Division 6 Rhoads Drive, Building 4 Utica, NY 13502 PH: 315-797-4449 FAX: 315-797-8024 EMAIL: chr...@gnlp.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Battery Safety
Chris: Is the battery a rechargeable? Have you tried disconnecting the 91K reisstor and measuring the resulting voltage increase? Doesn't make sense to me. Ralph Cameron EMC Consulting and Suppression of Consumer Electronics (After sale) - Original Message - From: Maxwell, Chris chr...@gnlp.com To: 'EMC-PSTC Internet Forum' emc-p...@majordomo.ieee.org Sent: Monday, September 25, 2000 11:30 AM Subject: Battery Safety All, We have inherited a design from a company which we purchased. The product is a handheld and can be operated from a pair of Alkaline batteries. Inside the unit, there is a 91 KOhm resistor across the + and - terminals of the batteries. Since the people who designed the instrument are long gone, some of my collegues have asked me if this resistor could be a safety feature. I can't think of any way this resistor would help the safety of the instrument. I did read through the safety test report; and I found no reference to this resistor being required. All it does is provide a constant drain on the battery (reducing battery life). It has been suggested to me that some designers put resistors across batteries to reduce the electrical noise in a product. To me a capacitor would be better for this because it wouldn't drain the battery while it was filtering. Even so, isn't a battery the ultimate capacitor? I'm just drawing a blank why anyone would do this. I'd love to recommend that we pull this resistor out because it's a pain to solder and it affects battery life. However, I don't want to sacrifice the safety of the product. Anybody want to take a guess at this one? Thanks. Chris Maxwell, Design Engineer GN Nettest Optical Division 6 Rhoads Drive, Building 4 Utica, NY 13502 PH: 315-797-4449 FAX: 315-797-8024 EMAIL: chr...@gnlp.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
