RE: [Repeater-Builder] Re: Recommendation - Vane Switch
If the blower is used to cool a tube pa the thermostat detection hardware is probably way to slow. I was assuming a SS PA, but maybe that was a mis-assumption. Many vane indicators are of the long arm micro switch type. Easy enough to make your own but you can probably find them through companies like McMaster, CH Sales Company, Grainger (all in Southern California) and many Heating Air Conditioning Supply Stores. I hate vane switches, having seen way too many failures over the years. Vanes breaking off, microswitches getting stuck due to all of the gunk that accumulates, etc. Good transmitters use differential pressure sensors to measure the difference between the two halves of the tube compartment. Too much differential and you've got a blockage in the tube fins or socket. Not enough differential and either the blower isn't running, the intake filter is clogged, or the chimney is blocked. I always monitor stack temperature too as a backup. For a SS PA, I still think a thermostat is the most reliable. I had a 5kW watt FM transmitter that somebody bypassed the air interlocks on. The squirrel cage blower lost a blade and jammed up. Looked like a miniature version of Cheryobyl in there after all was said and done...and off to the scrap yard it went (it was 30 years old and due for retirement anyway). --- Jeff
RE: [Repeater-Builder] Re: Recommendation - Vane Switch
Thanks guys for the interesting thoughts. All 6 of the PA's are solid state. They are the Quintron / Glenayre 90 watters. At 12:46 PM 7/23/2007, you wrote: If the blower is used to cool a tube pa the thermostat detection hardware is probably way to slow. I was assuming a SS PA, but maybe that was a mis-assumption. Many vane indicators are of the long arm micro switch type. Easy enough to make your own but you can probably find them through companies like McMaster, CH Sales Company, Grainger (all in Southern California) and many Heating Air Conditioning Supply Stores. I hate vane switches, having seen way too many failures over the years. Vanes breaking off, microswitches getting stuck due to all of the gunk that accumulates, etc. Good transmitters use differential pressure sensors to measure the difference between the two halves of the tube compartment. Too much differential and you've got a blockage in the tube fins or socket. Not enough differential and either the blower isn't running, the intake filter is clogged, or the chimney is blocked. I always monitor stack temperature too as a backup. For a SS PA, I still think a thermostat is the most reliable. I had a 5kW watt FM transmitter that somebody bypassed the air interlocks on. The squirrel cage blower lost a blade and jammed up. Looked like a miniature version of Cheryobyl in there after all was said and done...and off to the scrap yard it went (it was 30 years old and due for retirement anyway). --- Jeff Yahoo! Groups Links -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.14/912 - Release Date: 7/22/2007 7:02 PM
RE: [Repeater-Builder] Re: Recommendation - Vane Switch
I looked at the Quantar/Quantro diagram for their 100/125w PAs. They have one or two fans in them. The current is sensed as a voltage drop across a pair of 9.1 ohm resistors in the ground lead. This feeds two op-amps/comparators. If the current is too low or too high, either comparator output goes high and turns on a transistor through a diode OR gate. This feeds a mux chip along with a thermistor that senses PA temperature. The control module queries the mux chip and decides if the PA fans are working or not and/or if the PA is getting too hot. More details on request. Of course this doesn't necessarily tell you if the fans have failed yet are still drawing the same amount of current. If you have any kind of plenum setup, you can buy a small pressure sensor from Jameco and try to monitor the positive air pressure. It's better than nothing at all. You still may have to manipulate the output signal, and if the fans aren't on 100% of the time, you may want to gate the pressure signal with a fan on signal so you don't get a false failure when the fans aren't running. Bob M. == --- Adam C. Feuer [EMAIL PROTECTED] wrote: Thanks guys for the interesting thoughts. All 6 of the PA's are solid state. They are the Quintron / Glenayre 90 watters. At 12:46 PM 7/23/2007, you wrote: If the blower is used to cool a tube pa the thermostat detection hardware is probably way to slow. I was assuming a SS PA, but maybe that was a mis-assumption. Many vane indicators are of the long arm micro switch type. Easy enough to make your own but you can probably find them through companies like McMaster, CH Sales Company, Grainger (all in Southern California) and many Heating Air Conditioning Supply Stores. I hate vane switches, having seen way too many failures over the years. Vanes breaking off, microswitches getting stuck due to all of the gunk that accumulates, etc. Good transmitters use differential pressure sensors to measure the difference between the two halves of the tube compartment. Too much differential and you've got a blockage in the tube fins or socket. Not enough differential and either the blower isn't running, the intake filter is clogged, or the chimney is blocked. I always monitor stack temperature too as a backup. For a SS PA, I still think a thermostat is the most reliable. I had a 5kW watt FM transmitter that somebody bypassed the air interlocks on. The squirrel cage blower lost a blade and jammed up. Looked like a miniature version of Cheryobyl in there after all was said and done...and off to the scrap yard it went (it was 30 years old and due for retirement anyway). --- Jeff Boardwalk for $500? In 2007? Ha! Play Monopoly Here and Now (it's updated for today's economy) at Yahoo! Games. http://get.games.yahoo.com/proddesc?gamekey=monopolyherenow
Re: [Repeater-Builder] Re: Recommendation - Vane Switch
At 09:14 AM 07/23/07, you wrote: Many vane indicators are of the long arm micro switch type. Easy enough to make your own but you can probably find them through companies like McMaster, CH Sales Company, Grainger (all in Southern California) and many Heating Air Conditioning Supply Stores. A number of possible microswitches can easily be adapted to airflow vane switch applications. CH Sales sells or sold a lot of long arm units and numbers like the MICRO YZ-2RL come to mind as a possible option. C H Sales AKA C H Surplus is effectively no more. The owner has medical problems, and has decided to retire. After about a year of looking nobody wanted to buy the operation, so he has stopped buying, has slowly emptied the warehouse through the store, has sold the warehouse, and the store contents are selling. As of a week ago last friday the store is over 60% empty. Mike WA6ILQ
