[QUOTE=SubbyV-2;34459322]how do i get 12V to -10v?[/QUOTE]
Use a 1:1 transformator and then a negative voltage regulator.
Cathode resistor.
[editline]30th January 2012[/editline]
i.e. instead of trying to establish a negative supply, you stick a resistor to bias the cathode to some positive voltage and bias the grid to ground, so that the grid is negative [i]relative to the cathode[/i].
Either that, or drive the cathode high (but still lower than the anode) with an actual regulated supply. This is likely the better option, since this isn't a small-signal application and the voltage across a cathode bias resistor would vary greatly.
[url]http://en.wikipedia.org/wiki/File:Flyback_conventions.svg[/url]
And then ground the top part of the secondary circuit (to the right side of the diode) to achieve a negative voltage, and then use a negative voltage regulator. It's pretty easy really, you only need a transistor and a 1:1 mini-transformer and maybe add a third winding for a resonant switching if you're really fancy or just hook up an arduino to the transistor and find the best frequency.
You can find 1:1 coils in form of decoupling coils in PSUs, so if you have a dead one you should open it up and take a look inside: [url]http://i.imgur.com/oRW9s.png[/url]
It's still easier and simpler just to use resistors.
Why on earth would you waste the time and parts on something that is absolutely not needed, clearly the engineers axiom "Keep it simple, stupid" is not one that you subscribe to.
[QUOTE=Chryseus;34462053]It's still easier and simpler just to use resistors.
Why on earth would you waste the time and parts on something that is absolutely not needed, clearly the engineers axiom "Keep it simple, stupid" is not one that you subscribe to.[/QUOTE]
Well, it really depends on if he wants to get a real negative voltage or just hook up the tube up differently.
There's no reason to use 'real negative voltage'
Rather, there is no such thing as '[i]real[/i] negative voltage'. There's just relative to ground. And you don't need to worry about what things are relative to ground unless you're working on a device that communicates with other devices with single-ended signalling.
As a side note, the more I think about it, the more iffy a cathode resistor sound [i]in this particular case[/i]. I can't say I've used too many display tubes, but it seems like cathode current could vary wildly. Cathode bias resistors work in most amplifiers precisely because that is a small-signal AC application, so it's not really a huge problem. However, in this case it might be better to use a non-linear device to bias the cathode, like a Zener diode or a few LEDs.
Like this:
[img_thumb]http://i.imgur.com/uN6E0.png[/img_thumb]
After reading the datasheet I would say resistive (voltage divider) biasing of the cathode is more than adequate, if you bias the cathode at +10V the display should be zero with no grid input (see datasheet).
[url]http://www.r-type.org/pdfs/em87.pdf[/url]
Unusual datasheet.
The resistors on my UV-lamp reach 53°C, awesome
Going to order stuff this week to start making PCBs
I might even be able to offer you guys a low cost service once I get it up and running.
I made a boost converter out of someshit lying around and an arduino! but sadly, it only charges to 50V, must be the breakdown voltage of the diode?
Yepo, i need a better bloody diode. [url]http://www.sirectsemi.com/pdf/SB340~SB3100-DO27.pdf[/url]
this gives me idea, could i possibly use a power diode to restrict the capacitors potential to 250V?
[img]http://www.ieatnoobs.com/upload/IMG_1664.JPG[/img]
boost converters are easy.
Question:
How do I find out the torque that a servo is supplying when not moving?
Not when I'm telling it to go to an angle and it cannot, but when it has a certain angle and I'm telling it to keep that exact angle while a load is applied.
Is there some clever way to deduce that from power coming and going from the servo, or is there a special torque or tension sensor? Can you make a cheap tension sensor with just a thin wire under tension?
[QUOTE=Nikita;34481426]Question:
How do I find out the torque that a servo is supplying when not moving?
Not when I'm telling it to go to an angle and it cannot, but when it has a certain angle and I'm telling it to keep that exact angle while a load is applied.
Is there some clever way to deduce that from power coming and going from the servo, or is there a special torque or tension sensor? Can you make a cheap tension sensor with just a thin wire under tension?[/QUOTE]
[img]http://i.imgur.com/PTVdt.png[/img]
Torque = radius * perpendicular Force
Get one of those tiny little Force gauges with a simple spring inside that everybody knows from school.
*cough*My soldering iron just fell in the trash bin while on, now my room stinks :-C
I mean electronically. A servo is holding a certain weight that varies with time; I need to know the torque or perpendicular force, electronically, at every instant.
[QUOTE=Nikita;34481747]I mean electronically. A servo is holding a certain weight that varies with time; I need to know the torque or perpendicular force, electronically, at every instant.[/QUOTE]
Well, you could use a clip-on current sensor to measure the current and then measure the current with a set of know forces so you can interpolate a function for the force at a certain current
[QUOTE=DrLuke;34482066]Well, you could use a clip-on current sensor to measure the current and then measure the current with a set of know forces so you can interpolate a function for the force at a certain current[/QUOTE]
That simple? Why haven't I thought of this? Thanks.
[URL="http://i40.tinypic.com/zx0hoj.jpg"]New toy[/URL] arrived today; picked it up dirt cheap from a test-equipment surplus dealer. Now to get some practical experience with oscillators!
[QUOTE=Fuxed;34483347][URL="http://i40.tinypic.com/zx0hoj.jpg"]New toy[/URL] arrived today; picked it up dirt cheap from a test-equipment surplus dealer. Now to get some practical experience with oscillators![/QUOTE]
Name of the dealer?
[QUOTE=VistaPOWA;34484016]Name of the dealer?[/QUOTE]
Apologies but I think they're UK only; worth shooting them an email though I guess. It was [URL="http://www.stewart-of-reading.co.uk/index.htm"]Stewarts of Reading[/URL] if anyone's interested though.
[QUOTE=Fuxed;34484411]Apologies but I think they're UK only; worth shooting them an email though I guess. It was [URL="http://www.stewart-of-reading.co.uk/index.htm"]Stewarts of Reading[/URL] if anyone's interested though.[/QUOTE]
Hmm...
If I can't get that 50MHz EMG oscilloscope (for $10), I'll take a look into that.
Progress Report:
Got my parts in from Mouser, after a minor goof with the postal service.
And the chassis is coming along nicely, using an electrical hub box:
[IMG]https://sites.google.com/site/lonewolfscircuits/sitefiles/Chassis_Progress.JPG[/IMG]
Ordered an Arduino Mega! It will be delivered today or tomorrow! :D
[QUOTE=dije;34490440]Ordered an Arduino Mega! It will be delivered today or tomorrow! :D[/QUOTE]
Prepare to be swept into a world, a world of electronics, you will stray away from arduino.
Just finished my RRRNG (Really, Really Random Number Generator)
[t]http://localhostr.com/files/QYAjweD/IMG_20120130_230758.jpg[/t]
[t]http://localhostr.com/files/cZcVDhk/IMG_20120130_230739.jpg[/t]
[t]http://localhostr.com/files/xdb8c4g/IMG_20120130_230841.jpg[/t]
Ignore the capacitors, I put them there to make sure I won't lose them / for easy access, because I'll use them later.
[editline]1st February 2012[/editline]
[QUOTE=dije;34490440]Ordered an Arduino Mega! It will be delivered today or tomorrow! :D[/QUOTE]
Isn't this like the 7th hobby you took up this month?
How do you generate the random numbers?
[QUOTE=DrLuke;34492751]How do you generate the random numbers?[/QUOTE]
The arduino has a pseudo random number generator?
[QUOTE=DrLuke;34492751]How do you generate the random numbers?[/QUOTE]
Standard C random().
When I press the button, it stops generating numbers for a second and displays the latest result.
I am hoping to replace that button with a Geiger-Müller tube, stopping the generation at each detection. Background radiation is random.
Oh, I thought you implemented some real random number generator in hardware since you called it "Really, Really Random Number Generator"
[QUOTE=DrLuke;34492988]Oh, I thought you implemented some real random number generator in hardware since you called it "Really, Really Random Number Generator"[/QUOTE]
Well, you can't predict when I am going to press it.
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