SgtWookie:
I'm trying to build a hopefully simple tachometer to gauge fan speeds ranging from 0 to 30,000 RPMs. I am using the LM2907-8 with a desired output voltage of 0 to 10 volts (into my ADCs) and I've attached my schematic for your comments, if possible, along with the datasheet for the 28V fans.
I have tried to find a spice model for the 2907 to use pSpice in OrCAD but can't seem to find any. Would you know where i could find one?
There was one model that had a geocities link address that is no longer valid as it seems yahoo has closed all goecities accounts.
I added C24 as to remove a perceived DC offset based on what I interpreted from the fan datasheet where it said that its tachometer amplitude output is 5V ± 1v. I wasn't sure if they meant the amplitute is 5V with an offset of ±1v or the amplitude goes from 0-4volts to 0-6volts. If the latter, then I can remove R34 & C24. Can the 2907 work reliably with ground referenced devices? I am concerned about the comparator NOT switching if my input signal is within its voltage offset range.
Your help and comments are most welcome!
Thanks & Regards,
David Musoke
I'm trying to build a hopefully simple tachometer to gauge fan speeds ranging from 0 to 30,000 RPMs. I am using the LM2907-8 with a desired output voltage of 0 to 10 volts (into my ADCs) and I've attached my schematic for your comments, if possible, along with the datasheet for the 28V fans.
I have tried to find a spice model for the 2907 to use pSpice in OrCAD but can't seem to find any. Would you know where i could find one?
There was one model that had a geocities link address that is no longer valid as it seems yahoo has closed all goecities accounts.
I added C24 as to remove a perceived DC offset based on what I interpreted from the fan datasheet where it said that its tachometer amplitude output is 5V ± 1v. I wasn't sure if they meant the amplitute is 5V with an offset of ±1v or the amplitude goes from 0-4volts to 0-6volts. If the latter, then I can remove R34 & C24. Can the 2907 work reliably with ground referenced devices? I am concerned about the comparator NOT switching if my input signal is within its voltage offset range.
Your help and comments are most welcome!
Thanks & Regards,
David Musoke
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