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Old 10-31-2007, 11:59 AM #1
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Default another addition to ddl's circuit

I was previously thinking about using a 7806 or zener regulator to supply DDL's circuit then tonight had another idea which may prevent over voltage should the LD disconnect from the circuit (ie giving full charge to capacitor) would be to put the zener/transistor configuration after the current regulation

A very detailed explanation can be found here http://www.satcure-focus.com/tutor/page5.htm

although this is based on a 5v circuit we could get stable regulation by using a 3v6 zener (have not worked out exact resistance yet)

The idea I had was replace the LD in DDL's circuit with that of the one shown in the link set for 3v output then connect the LD to that if the LD was to disconnect and then reconnect it would protect the LD from damage I will try this over the weekend however I still think that I would need some form of constant load over the output like a 1k resistor or similar (will try with/without)

The advantages would be a larger varying input voltage to the lm317 as current is regulated and voltage regulation coming at the later stage of the circuit which would give a constant 3v to the LD

I used to be very much of an experimenter with electronics but for the last 10 or so years not really done much so a little rusty on some things but it is slowly coming back heck I used to fix TV's as a kid when you would still pay $50 for a black and white with valves (if you younger ppl here are lost try looking on Noah's ark lol) and now I am looking at wafer thin circuit boards with tiny SMD's with 2 or 3 pins per mm tell your grandchildren to look in museums for this in 50 years or so however I wont be using SMD as I dont have steady enough hand etc etc ...

anyway thats enought ranting will build (hopefully) this circuit and try it out



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Old 10-31-2007, 01:31 PM #2
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Default Re: another addition to ddl's circuit

I have thought about a zener but recall that that 3.6V zener would have to sink almost 1Watt at 250mA drive current.

Quote:
Originally Posted by numberonekiwi
I was previously thinking about using a 7806 or zener regulator to supply DDL's circuit then tonight had another idea which may prevent over voltage should the LD disconnect from the circuit (ie giving full charge to capacitor) would be to put the zener/transistor configuration after the current regulation

A very detailed explanation can be found here http://www.satcure-focus.com/tutor/page5.htm

although this is based on a 5v circuit we could get stable regulation by using a 3v6 zener (have not worked out exact resistance yet)

The idea I had was replace the LD in DDL's circuit with that of the one shown in the link set for 3v output then connect the LD to that if the LD was to disconnect and then reconnect it would protect the LD from damage I will try this over the weekend however I still think that I would need some form of constant load over the output like a 1k resistor or similar (will try with/without)

The advantages would be a larger varying *input voltage to the lm317 as current is regulated and voltage regulation coming at the later stage of the circuit which would give a constant 3v to the LD

I used to be very much of an experimenter with electronics but for the last 10 or so years not really done much so a little rusty on some things but it is slowly coming back heck I used to fix TV's as a kid when you would still pay $50 for a black and white with valves (if you younger ppl here are lost try looking on Noah's ark lol) and now I am looking at wafer thin circuit boards with tiny SMD's with 2 or 3 pins per mm tell your grandchildren to look in museums for this in 50 years or so however I wont be using SMD as I dont have steady enough hand etc etc ...

anyway thats enought ranting will build (hopefully) this circuit and try it out
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Old 10-31-2007, 10:32 PM #3
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Default Re: another addition to ddl's circuit

hi chimo I have looked at data sheets for the 1n4729 and it shows Iz=69mA and the BZX55C3v6 having only 5mA would I be correct in thinking that that is the current needed for reverse breakage breakdown to make this device regulate if that is the case then the 1n4729 is definitely out of the question but the BZX55C3v6 still looks plausible

I have worked out that a 5.5 ohm resistor would be needed for the 1n but a 29 ohm resistor with the bzx assuming a 7v input to ddl's circuit giving a 4v output minimum required for regulation there fore with those resistance 0.4/5.5=73mA not to good with the bzx it would be 0.4/29=14mA not to bad now now lets assume we feed ddl's circuit with 8.4 v the output would be 5.4v and we can work out the regulation current 8.4-3.6=4.8 v

so 4.8/5.5=872mA terrible not even worth while thinking about it 4.8/29=166 mA about what the LD would draw =50% efficiency working on my formula last night (I shouldn't think electronics late at night) so totally blows my idea of this out of the garbage pile oh well was just a thought
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Old 11-01-2007, 10:49 PM #4
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Default Re: another addition to ddl's circuit

Good thinking nonetheless kiwi

I like the idea of having a 'valve' that can be placed in there easily... but I haven't found one simple enough to implement... and any solution we add will result in drift current... thus less efficiency... thus wasted energy... thus unreliable output based on the current limiting existent in the LM317. All of which can be easily avoided just by making sure the Cap is discharged prior to connecting and making sure you solder the cap as close to the LD as possible

--DDL
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