DHT Heater using VCCS - PCB or Kit (Possible Group buy)
- jack
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#31
Hi Andrew - only just really read this thread - what approach are you using - I've been playing with something along the Tent Labs line but using high-side current sensing (instead of low) and instrumentation amps (AD8274 / AD8603) with a TIP121 at the moment - also using an ultra-low-noise reference voltage - not an expensive, though slightly exotic, design...
All probably overkill, but they are low-cost and extremely low noise, as well as being temperature stabilised.
I like the Tent Labs over-temperature safety too, but I fail to see why its needed if the design of the VCCS is right...
All probably overkill, but they are low-cost and extremely low noise, as well as being temperature stabilised.
I like the Tent Labs over-temperature safety too, but I fail to see why its needed if the design of the VCCS is right...
Vivitur ingenio, caetera mortis erunt
#32
Hi Nick,
Its a twin op amp design using a cost effective generic rail to rail twin op amp, current is sensed in the tail of the CCS.
I plan to use a TL431 as the Vref as it can be set with just two resistors, its pretty cheap and absolute accuracy isn't all that important. I'm not wedded to the TL431; it just seemed a practical solution to allow folk to run at various voltages.
The image attched is the best I've manged yet in terms of spectrum. I tried powering the op amp from its own (bench) supply, it was actually worse.
Andrew
Its a twin op amp design using a cost effective generic rail to rail twin op amp, current is sensed in the tail of the CCS.
I plan to use a TL431 as the Vref as it can be set with just two resistors, its pretty cheap and absolute accuracy isn't all that important. I'm not wedded to the TL431; it just seemed a practical solution to allow folk to run at various voltages.
The image attched is the best I've manged yet in terms of spectrum. I tried powering the op amp from its own (bench) supply, it was actually worse.
Andrew
Analogue, the lost world that lies between 0 and 1.
- Mike H
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#33
This may be a spanner in the works, but I'd forgotten all about it but just remembered and found it again. First found this over a year ago. Design by Kees Soeters?
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- jack
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#34
Indeed - http://members.ziggo.nl/techgraphix/PDF ... Supply.pdfMike H wrote:This may be a spanner in the works, but I'd forgotten all about it but just remembered and found it again. First found this over a year ago. Design by Kees Soeters?
Main pages for his astonishing 300B amp - http://members.ziggo.nl/techgraphix/Amplifier.html
I remember coming across this years ago (2005/2006?) and being amazed at the workmanship - a bit "blingy" for my tastes, but very impressive work ntl... e.g. having your star earth stud hallmarked (even though no-one can see it) because its made from 99.999% pure silver. Sheer lunacy
Last edited by jack on Sun Mar 03, 2013 2:04 pm, edited 1 time in total.
Vivitur ingenio, caetera mortis erunt
#35
Some similarities, but that just confirms we're on the right track.Mike H wrote:This may be a spanner in the works, but I'd forgotten all about it but just remembered and found it again. First found this over a year ago. Design by Kees Soeters?
Andrew
Analogue, the lost world that lies between 0 and 1.
- Mike H
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#36
Fairy nuff!
Think you were asking me about this a while ago, or somebody was, as an alternative to e.g. the Rod Coleman method insofar self Voltage stabilisation could be incorporated as well.
Think you were asking me about this a while ago, or somebody was, as an alternative to e.g. the Rod Coleman method insofar self Voltage stabilisation could be incorporated as well.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
#37
I reckon the 7.5v should be fine, I used 9v RMS for 5v out, which gives 12v smoothed DC or about 7v working overhead between Vin and Vout. I may try this out as a test case, I might be able to get the required voltage down a bit more, dunno, yet, its all work in progress.Andrew, for 2.5V out (2A3) what would be the volts in required, roughly....I have 5.5V and 7.5V options with my existing TX.
Andrew
Analogue, the lost world that lies between 0 and 1.
#38
Thanks Andrew.Andrew wrote:I reckon the 7.5v should be fine, I used 9v RMS for 5v out, which gives 12v smoothed DC or about 7v working overhead between Vin and Vout. I may try this out as a test case, I might be able to get the required voltage down a bit more, dunno, yet, its all work in progress.Andrew, for 2.5V out (2A3) what would be the volts in required, roughly....I have 5.5V and 7.5V options with my existing TX.
Andrew
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#40
Megastar!
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- Dave the bass
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#42
I finally managed to dislodge the digit and here's prototype PCB #1.
I found a few things layout-wise I want to change so its been worthwhile exercise; testing will commence this coming week.
Andrew
I found a few things layout-wise I want to change so its been worthwhile exercise; testing will commence this coming week.
Andrew
Analogue, the lost world that lies between 0 and 1.
- IslandPink
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#44
Top work young fella !
It's definitely very topical for me as I'm going to be trying 4P1L as a driver for 300B pretty soon .
It's definitely very topical for me as I'm going to be trying 4P1L as a driver for 300B pretty soon .
"Once you find out ... the Circumstances ; then you can go out"