You can make a -12V (actually more like -11V) source with a 555 timer and a few caps/diodes in a charge pump circuit. It'll only supply a little over a tenth of an amp (the 555 is rated for 200mA) and there might be some ripple, but having a negative supply really makes op-amp circuits (and just about anything that requires biasing) simpler.
[QUOTE=ROBO_DONUT;31413587]You can make a -12V (actually more like -11V) source with a 555 timer and a few caps/diodes in a charge pump circuit. It'll only supply a little over a tenth of an amp (the 555 is rated for 200mA) and there might be some ripple, but having a negative supply really makes op-amp circuits (and just about anything that requires biasing) simpler.[/QUOTE]
Good idea, he could also split the 12V rail into +-6V, which depending how it is split could still provide significant current.
[QUOTE=Chryseus;31414708]Good idea, he could also split the 12V rail into +-6V, which depending how it is split could still provide significant current.[/QUOTE]
That's a much better solution if need a lot of current without ripple, but it also means that your virtual ground won't be the same as earth ground which may or may not be a problem depending on your application (mostly for interconnected systems). Of course caps/transformers/opto-isolators solve that problem.
My father's friend was throwing out old stuff, and he gave me an old 80s Russian oscilloscope, analog. It's in pretty much mint condition, the manual that comes with it is still in shrink wrap. Shame I won't get to use it for another 2 weeks as I'm leaving for camp.
[QUOTE=amazer97;31443269]My father's friend was throwing out old stuff, and he gave me an old 80s Russian oscilloscope, analog. It's in pretty much mint condition, the manual that comes with it is still in shrink wrap. Shame I won't get to use it for another 2 weeks as I'm leaving for camp.[/QUOTE]
Nice ! take some pictures of it when you can.
[QUOTE=amazer97;31443269]My father's friend was throwing out old stuff, and he gave me an old 80s Russian oscilloscope, analog. It's in pretty much mint condition, the manual that comes with it is still in shrink wrap. Shame I won't get to use it for another 2 weeks as I'm leaving for camp.[/QUOTE]
Does it use vacuum tubes?
I got an early birthday present from my brother :D
(Or, well, I will be receiving it. It's coming in the mail)
[img]http://www.adafruit.com/images/large/toolbox_LRG.jpg[/img]
([url=http://adafruit.com/products/136]this[/url])
Jackpot! I also was given a MintyBoost kit to make!
Rigol DS1052E just arrived, I'm very happy with it so far.
Just built a small electret mic amplifier with an op-amp to test it:
[img]http://i.imgur.com/YubXZ.png[/img]
For those who can't read, blue = input, yellow = output.
[QUOTE=Chryseus;31487803]Rigol DS1052E just arrived, I'm very happy with it so far.
Just built a small electret mic amplifier with an op-amp to test it:
[img]http://i.imgur.com/YubXZ.png[/img]
For those who can't read, blue = input, yellow = output.[/QUOTE]
I would so abuse that
[img]http://i.imgur.com/Cng93.png[/img]
It was too late when I noticed that my voltage regulator was smoking off.
[QUOTE=DrLuke;31492796][img]http://i.imgur.com/Cng93.png[/img]
It was too late when I noticed that my voltage regulator was smoking off.[/QUOTE]
Ouch. My breadboard has suffered orange juice and coffee, getting a little difficult to insert stuff into it.
Oh man, that photo reminds me of some of the breadboards from computer engineering in high school.
Oh well, now your breadboard has a battlescar and a story to tell.
[editline]fakelol[/editline]
Can someone help me out with a simple transistor amplifier? I pulled an electret mic off of my old FM transmitter from school, and I can't for the life of me get a signal out of it, though I'm fairly sure that's because it's too weak for me to measure.
[QUOTE=Lapsus;31496979]Oh man, that photo reminds me of some of the breadboards from computer engineering in high school.
Oh well, now your breadboard has a battlescar and a story to tell.
[editline]fakelol[/editline]
Can someone help me out with a simple transistor amplifier? I pulled an electret mic off of my old FM transmitter from school, and I can't for the life of me get a signal out of it, though I'm fairly sure that's because it's too weak for me to measure.[/QUOTE]
[url]http://en.wikipedia.org/wiki/Transistor#Transistor_as_an_amplifier[/url]
[QUOTE=Lapsus;31496979]Can someone help me out with a simple transistor amplifier? I pulled an electret mic off of my old FM transmitter from school, and I can't for the life of me get a signal out of it, though I'm fairly sure that's because it's too weak for me to measure.[/QUOTE]
You need to power it through a resistor. Those electret microphones generally have a JFET built-in to help amplify the signal. All you need to do is provide power and a load resistor, generally in the range of a few kOhms (2.2k is a good place to start). Higher resistor values produce more gain, as with all common-source amplifiers.
Make sure you get the polarity right. You take the output from between the load resistor and the electret, generally coupled through a capacitor.
[editline]3rd August 2011[/editline]
Hopefully you didn't already hook it straight up to power or anything. Powering it without a load would probably cause permanent damage.
Thanks for the help, ROBO_DONUT. I don't exactly know how to do anything useful with the signal I'm getting out of the mic yet, but I am at least getting a signal.
[QUOTE=Lapsus;31501929]Thanks for the help, ROBO_DONUT. I don't exactly know how to do anything useful with the signal I'm getting out of the mic yet, but I am at least getting a signal.[/QUOTE]
You could build a class-D amplifier out of 3 op-amps and have a speaker outputting whatever the microphone picks up.
The use of that is ???.
Got a Wii Nunchuk working with my Arduino.
[media]http://www.youtube.com/watch?v=491N-35HS64[/media]
That took for-fucking-ever.
[QUOTE=i300;31544586]Got a Wii Nunchuk working with my Arduino.
[media]http://www.youtube.com/watch?v=491N-35HS64[/media]
That took for-fucking-ever.[/QUOTE]
Had a friend of mine do that once, except he managed to control two servos attached to each other for a 2-axis device. Never did anything else with it though, as much as he tinkers he's a lazy bastard. :v:
konami code is best code
Yeah I finished my accelerometer thingy
[media]http://www.youtube.com/watch?v=Xg7vO1Vk7qM[/media]
I had some fun building a simple 555 charge pump voltage inverter.
Going to improve it to provide a positive and negative 2 x Vin and build my own RS232 level shifter.
[b]Schematic[/b]
[img]http://i.imgur.com/6fidv.png[/img]
[b]Results[/b]
[img]http://i.imgur.com/yUFII.png[/img]
[QUOTE=DrLuke;31545522]Yeah I finished my accelerometer thingy[/quote]
Send the data to a computer and write something to draw a nice graph.
After building 1 double h bridge I decided to just order 3 ic's from bitsbox. Have around a week until those arrive so in the meanwhile I am going to build a frame for the cnc machine, should I post pictures of the building process ?
[QUOTE=quincy18;31565212]After building 1 double h bridge I decided to just order 3 ic's from bitsbox. Have around a week until those arrive so in the meanwhile I am going to build a frame for the cnc machine, should I post pictures of the building process ?[/QUOTE]
Yes, you should post pictures.
Was working on amplifying the output of a PMA4601M IR receiver to 0V-5V, but accidentally made it emit magic blue smoke. Oh well, I'll buy a proper TTL-level IR detector tomorrow (this one was found in my junk box). v:v:v
[QUOTE=i300;31461145][img]http://www.adafruit.com/images/large/toolbox_LRG.jpg[/img][/QUOTE]
el cheapo chinese Mastech multimeter owners represent!
[img]http://i.imgur.com/AxN99l.jpg[/img]
I'm building a computer system for my large-scale UAV and I decided on Gumstix (Is there anything else?). So I'm wondering how to control the servos using a embedded system like Gumstix. Hope someone answers.
[QUOTE=Mr.T;31660184]I'm building a computer system for my large-scale UAV and I decided on Gumstix (Is there anything else?). So I'm wondering how to control the servos using a embedded system like Gumstix. Hope someone answers.[/QUOTE]
PWM (pulse width modulation). Have a digital (TTL, 0-5V) output send out pulses every 20ms to the control wire of the servo (usually the middle one of the three, the other two being GND/0V and 5V). The pulse width is what sets the angle of the servo. A pulse width of 1ms will set the servo to 0 degrees, a pulse width of 2ms will set the servo to 180 degrees. Any other angle you want to obtain is proportional to the max time values I cited. So, for example, a 1.5ms pulse will set the angle to 90 degrees. It's that easy. Usually you don't even have to drive the outputs with transistors, as the current consumed by a servo on the control wire is very small.
Now, how to implement that on a Gumstix system is something I have no idea about - I guess there are some GPIO ports that you can use?
Also, how do I connect Arduino with Gumstix?
Does Gumtix have UART? If so use that?
[QUOTE=benjojo;31666793]Does Gumtix have UART? If so use that?[/QUOTE]
Thanks, I also found out that gumstix uses i2c.
I have an old broken harddrive stripped apart. Time to fuck with the motor :v:.
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