Sunbeam heated blanket controller
I recently purchased a Sunbeam electric blanket. It
works ok except that its lowest setting is a bit too high for my liking and I am looking for ways to reduce its output. I have read online that they use a heating wire with a high positive temperature coefficient of resistance so that it is not only a heater but also a temperature sensor. I have monitored the current draw. When turned on the current starts at 2 amps and gradually drops to near an amp before the controller switches off. Has anyone opened up one of these controllers? The product description says it is solid state and noiseless and that if there is an error condition the controller light will flash. It sounds like it might have a microprocessor but I am reluctant to open up the controller on a brand new item which has a 5 year warranty if there is nothing inside which I can tweak to lower the lowest setting. My thinking now is that if it is microprocessor controlled it would be difficult to modify. My first thought was to lower the input voltage but I think the microprocessor would be able to compensate. Any ideas? thanks kw ----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= - Total Privacy via Encryption =--- |
Sunbeam heated blanket controller
Ken Wright wrote:
I recently purchased a Sunbeam electric blanket. It works ok except that its lowest setting is a bit too high for my liking and I am looking for ways to reduce its output. I have read online that they use a heating wire with a high positive temperature coefficient of resistance so that it is not only a heater but also a temperature sensor. I have monitored the current draw. When turned on the current starts at 2 amps and gradually drops to near an amp before the controller switches off. Has anyone opened up one of these controllers? The product description says it is solid state and noiseless and that if there is an error condition the controller light will flash. It sounds like it might have a microprocessor but I am reluctant to open up the controller on a brand new item which has a 5 year warranty if there is nothing inside which I can tweak to lower the lowest setting. My thinking now is that if it is microprocessor controlled it would be difficult to modify. My first thought was to lower the input voltage but I think the microprocessor would be able to compensate. Any ideas? thanks kw ----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= - Total Privacy via Encryption =--- There must be a PTC (positive Temperature Coefficient) resistor in it. Measure the value are room temperature and and place a small value R in series with it to off set the calibration so that it'll operate at a cooler level. Or, reposition the PTC closer to a heating wire, it could of slip out of the original position. http://webpages.charter.net/jamie_5" |
Sunbeam heated blanket controller
Use your variac
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Sunbeam heated blanket controller
On Wed, 24 Dec 2008 17:15:19 -0700, Ken G. wrote:
Use your variac If it is a true thermostat I don't believe lowering the voltage will help. kw ----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= - Total Privacy via Encryption =--- |
Sunbeam heated blanket controller
Ken Wright writes:
On Wed, 24 Dec 2008 17:15:19 -0700, Ken G. wrote: Use your variac If it is a true thermostat I don't believe lowering the voltage will help. To the original poster: Are you sure the blanket is working properly. The lowest setting on the Sunbeam blankets I've had was next to no heat. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
Sunbeam heated blanket controller
The lowest setting on the Sunbeam blankets I've had
was next to no heat. I have both a Snbeam blanket and "throw", and the Low setting is, indeed, low. |
Sunbeam heated blanket controller
On Thu, 25 Dec 2008 08:58:28 -0500, Sam Goldwasser wrote:
Ken Wright writes: To the original poster: Are you sure the blanket is working properly. The lowest setting on the Sunbeam blankets I've had was next to no heat. I've never had an electric blanket before so I don't know what `working properly' is. It definitely gets much warmer on higher settings so I assume it is normal. I put it on a variac at 90 volts last night and it may have lowered the heat output a bit. It abruptly ceases operation at about 40 volts (light goes out and it won't power on). kw ----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= - Total Privacy via Encryption =--- |
Sunbeam heated blanket controller
On Wed, 24 Dec 2008 18:39:49 -0500, Jamie
t put finger to keyboard and composed: Ken Wright wrote: I have read online that they use a heating wire with a high positive temperature coefficient of resistance so that it is not only a heater but also a temperature sensor. I have monitored the current draw. When turned on the current starts at 2 amps and gradually drops to near an amp before the controller switches off. There must be a PTC (positive Temperature Coefficient) resistor in it. Measure the value are room temperature and and place a small value R in series with it to off set the calibration so that it'll operate at a cooler level. Or, reposition the PTC closer to a heating wire, it could of slip out of the original position. The heating element itself provides the PTC resistance. If the PTC resistor were external to the blanket (ie inside the controller), then initially it would present a short circuit (or very low resistance), in which case the blanket would see 110VAC at 2A. If the current then gradually decreases to 1A, this would mean that the PTC would be dissipating 55W (= 55VAC @ 1A). - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
Sunbeam heated blanket controller
On Wed, 24 Dec 2008 16:07:47 -0600, Ken Wright
put finger to keyboard and composed: I recently purchased a Sunbeam electric blanket. It works ok except that its lowest setting is a bit too high for my liking and I am looking for ways to reduce its output. I have read online that they use a heating wire with a high positive temperature coefficient of resistance so that it is not only a heater but also a temperature sensor. I have monitored the current draw. When turned on the current starts at 2 amps and gradually drops to near an amp before the controller switches off. Here are two Sunbeam patents for PTC heating wire and one for PTC temperature sensing wi http://www.google.com/patents/pdf/Bl...We ftrxVZtgZQ http://www.google.com/patents/pdf/El...t2tVm2PWmyvU7A http://www.google.com/patents/pdf/Te...RJ yPn382DRbA Here are other Sunbeam electric blanket patents: http://www.google.com/patents?as_drr...&sa=N&start=20 Is there a patent number on your appliance? Has anyone opened up one of these controllers? The product description says it is solid state and noiseless ... I'm guessing it uses a triac with a zero voltage switching control circuit. ... and that if there is an error condition the controller light will flash. It sounds like it might have a microprocessor but I am reluctant to open up the controller on a brand new item which has a 5 year warranty if there is nothing inside which I can tweak to lower the lowest setting. My thinking now is that if it is microprocessor controlled it would be difficult to modify. My first thought was to lower the input voltage but I think the microprocessor would be able to compensate. Any ideas? thanks kw As others have suggested, it may be that your blanket is not working properly. The min-max current difference (1A versus 2A) seems inadequate, but then you need to determine whether the duty cycle remains constant or not. I expect that you will find that your blanket has a PTC heating element, and that its controller operates more like a thermostat (or simmerstat) than a dimmer. It seems logical to me for a temperature controller with 10 settings, say, to turn on the heat for 1 second and off for 9 seconds on the lowest setting, and on for 9 seconds and off for 1 sec on the second highest setting. But I'm only guessing. AFAICS, a dimmer control would be unnecessary due to the thermal inertia (?) of the heating element, and it would also generate EMI. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
Sunbeam heated blanket controller
On Thu, 25 Dec 2008 18:31:35 -0000, Meat Plow wrote:
On Thu, 25 Dec 2008 08:58:28 -0500, Sam Goldwasser wrote: Ken Wright writes: On Wed, 24 Dec 2008 17:15:19 -0700, Ken G. wrote: Use your variac If it is a true thermostat I don't believe lowering the voltage will help. To the original poster: Are you sure the blanket is working properly. The lowest setting on the Sunbeam blankets I've had was next to no heat. Also have a Sunbeam and it has infinite control. Although mine is their better blanket priced around $69 US for a queen. And I don't have an electric blanket, ya bunch of cissies! -- http://www.petersparrots.com http://www.insanevideoclips.com http://www.petersphotos.com Bad or missing mouse. Spank the cat (Y/N)? |
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