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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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12th Mar 2017, 5:27 pm | #21 |
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Re: Dropping 40V Down to 9V volts
You won't need to heatsink it if the current is low.
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12th Mar 2017, 5:28 pm | #22 |
Octode
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Re: Dropping 40V Down to 9V volts
ah ok but I would be able to bolt it to the chassis?
Gary |
12th Mar 2017, 5:32 pm | #23 |
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Re: Dropping 40V Down to 9V volts
No, not without an insulator. It's connected to the output pin as with similar voltage regs.
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12th Mar 2017, 6:06 pm | #24 |
Octode
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Re: Dropping 40V Down to 9V volts
Gary:
If its only pulling say 10 or 20mA theres no need to bolt it down it won't get hot enough to worry about. I'd assume you'll use a bit of veroboard/stripboard to mount it and it's associated components on so why not just bolt the wee bit of board down on a short standoff? Heck a nut would likely be thick enough to keep the board clear of the chassis. I'd use the recommended circuit with decoupling capacitors on input and output. It could save annoying oscillations. A. |
12th Mar 2017, 7:39 pm | #25 |
Octode
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Re: Dropping 40V Down to 9V volts
The LM317AHV would also fit the bill. Its a high voltage variant of the well known LM317 and has a 60 volt input to output differential rating.
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12th Mar 2017, 8:12 pm | #26 |
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Re: Dropping 40V Down to 9V volts
When you're bringing the voltage down a long way and only taking a light current, watch out for the current taken in the voltage programming resistors - typically 10mA because this can take as much power and create as much heat as the wanted output, if the output current is similar.
There are some regulators with particularly low currents on their reference pins, so you can scale down the programming resistor current and make the thing a good bit cooler. David
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12th Mar 2017, 8:55 pm | #27 | |
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Re: Dropping 40V Down to 9V volts
Quote:
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12th Mar 2017, 9:08 pm | #28 |
Octode
Join Date: Feb 2009
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Re: Dropping 40V Down to 9V volts
"How much current does the tuner take"
I do not actually know it is run off a 2 watt 1K resistor Gary |
12th Mar 2017, 10:24 pm | #29 |
Nonode
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Re: Dropping 40V Down to 9V volts
Hi
CPC have the TL483 voltage regulator available singly. http://cpc.farnell.com/texas-instrum...rfnonsku=false Regards Symon |
12th Mar 2017, 11:25 pm | #30 |
Octode
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Re: Dropping 40V Down to 9V volts
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13th Mar 2017, 8:10 am | #31 |
Dekatron
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Re: Dropping 40V Down to 9V volts
The LM317AVH goes up to 57v, output is connected to the body like most 3 pin adjustable regulators.
Andy.
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13th Mar 2017, 8:37 am | #32 | |
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Re: Dropping 40V Down to 9V volts
Quote:
However, there is a minimum load of 15mA. Many people (me sometimes!) achieve this by using low-value programming resistors, so that the output doesn't rise off-load. But, if you have a permanent load, the problem goes away. So in this application, just don't have a big output capacitor, disconnect your FM tuner with the 40V still supplied, and then reconnect it. Or if you think you might, have a Zener diode across the output of a couple of volts higher than the programmed output voltage, which will hold things down off-load, but have no effect on-load. Dr Wobble and Mooly's suggestion of LM317HV would also be a good candidate, the same applies here too! |
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23rd Mar 2017, 4:34 pm | #33 |
Octode
Join Date: Feb 2009
Location: Cornwall, UK.
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Re: Dropping 40V Down to 9V volts
I bought a TL783 and it works perfectly so thanks to all who contributed and gave advice.
Gary |