[quote]For some reason DrLuke kept rating my posts dumb after his "i2c" post on the last page so I started rating him dumb as well.[/quote]
[quote]I have no idea, they started it, so I rated back[/quote]
Mutually Agreed Dumbness
Let's be grown ups and stop it then
[QUOTE=Nikita;33472198]So I made a v-usb circuit on a breadboard with ATmega16... Haven't tested yet.
I have no idea what I'm going to do when it doesn't work. Any tips?[/QUOTE]
Debug in Linux, 'lsusb -v' helps enormously.
Since it's nearing Christmas I've decided to do a special Christmas electronics project.
I can't think of anything particularly Christmas themed so I'm just going to do an AM radio.
Everyone else is welcome to join in, there is no prize unless someone wants to donate something.. cake maybe ?
Remote controlled Christmas lights.
Motion sensing Christmas lights.
AM transmitter to talk to Chryseus via his AM radio.
Remote Controlled AM transmitter to talk to Chryseus motion sensing Christmas lights?
Audio Controlled Christmas lights from random AM radio pickup.
Motion of people passing by determines AM pickup frequency via an arbitrary algorithm which in turn controlls Chryseus' christmas lights
So I have a cheap clip-on mic for skype and various other voip things and it is insanely quiet, meaning I have to boost it by about 30db in windows to get it to an acceptable volume. This, however, adds a lot of noise. I'm just guessing here but if the amplification in windows is purely software, would I get less noise if I built a pre-amp and leave the gain at 0 in windows?
Follow up question, what's a good source for info on the specifics on how to do this? I've learned in school some about amplifiers but little about how to apply that knowledge.
[QUOTE=chipset;33501081]So I have a cheap clip-on mic for skype and various other voip things and it is insanely quiet, meaning I have to boost it by about 30db in windows to get it to an acceptable volume. This, however, adds a lot of noise. I'm just guessing here but if the amplification in windows is purely software, would I get less noise if I built a pre-amp and leave the gain at 0 in windows?
Follow up question, what's a good source for info on the specifics on how to do this? I've learned in school some about amplifiers but little about how to apply that knowledge.[/QUOTE]
Maybe.
The thing is, with electret microphones, they've basically got half of an amplifier built-in. It's a little electro-mechanical device with a N-JFET attached. The source of the JFET is connected to ground (the sleeve of the TRS plug) and the drain is connected to the tip/ring of the plug. If you've done any analog stuff before, you should be familiar with the common-source amplifier (analogous to the common-emitter amplifier, but with a FET instead of a BJT). This is basically just a common-source amplifier without the voltage supply or load resistor. The device receiving input provides power to the microphone through this load resistor, and takes the voltage from between the resistor and the JFET (in the mic). The gain of this (pre-)amplifier is proportional to the value of this resistor.
So half of the amp is already there. It's just a matter of figuring out the right value and providing power. You will, of course, need to use line-in instead of the mic input on your sound card if you're doing the amplification externally and couple the amp through a capacitor so you don't blow anything up.
30dB is a lot, though. You might still need an extra amp. The resistor in the pre-amp is typically about 2.2kohm, line-in impedance is around 10kohm, so you don't have a huge amount of wiggle room.
For all the years I have worked with old computers and electronics I am amazed I ahve never required the use of an EPROM burner until now.
I picked up an Apple II "Sandwich II" SCSI card that I'll use with a modified 40mb ProFile hard drive but it's missing the 27C256 ROM oddly.
Sold some hardware and went over to ebay and bought a [url=http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150711241696]Willem PCB 5.0 programmer[/url].
[img]http://www.sivava.com/img-product/EPROM_Pro_04/pcb4-5c_construction-EBay.jpg[/img]
For $40 shipped it sure can do a hell of a lot of different chips. I should make a custom enclosure for it and buy some more TEXTOOL sockets.
I'm suprised how cheap this thing was. I'm used to seeing programmers for $80-$300.
555 timer without caps:
[t]http://i56.tinypic.com/k15bbc.png[/t]
555 timer with 10 uF across the power rail:
[t]http://i52.tinypic.com/11hbc52.png[/t]
Does anybody know how I can get rid of the rest of the jitter?
[QUOTE=MIPS;33527912]For all the years I have worked with old computers and electronics I am amazed I ahve never required the use of an EPROM burner until now.
I picked up an Apple II "Sandwich II" SCSI card that I'll use with a modified 40mb ProFile hard drive but it's missing the 27C256 ROM oddly.
Sold some hardware and went over to ebay and bought a [url=http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150711241696]Willem PCB 5.0 programmer[/url].
[img]http://www.sivava.com/img-product/EPROM_Pro_04/pcb4-5c_construction-EBay.jpg[/img]
For $40 shipped it sure can do a hell of a lot of different chips. I should make a custom enclosure for it and buy some more TEXTOOL sockets.
I'm suprised how cheap this thing was. I'm used to seeing programmers for $80-$300.[/QUOTE]
Wow that's cheap. If it turns out to be any good let us know!
[QUOTE=DrLuke;33528338]555 timer without caps:
[t]http://i56.tinypic.com/k15bbc.png[/t]
555 timer with 10 uF across the power rail:
[t]http://i52.tinypic.com/11hbc52.png[/t]
Does anybody know how I can get rid of the rest of the jitter?[/QUOTE]
You have any other circuits on your board?
Are you running this on a filtered supply(Sometimes on my circuits even with a buncha caps, full-bridge rectifier and good regulator, the 60Hz hum still seeps in :P)
Also, are you using the old bipolar version(NE555) or the MOS version(eg TLC555)?
[QUOTE=LoneWolf_Recon;33530619]You have any other circuits on your board?
Are you running this on a filtered supply(Sometimes on my circuits even with a buncha caps, full-bridge rectifier and good regulator, the 60Hz hum still seeps in :P)
Also, are you using the old bipolar version(NE555) or the MOS version(eg TLC555)?[/QUOTE]
I've powered it with USB, so it should be a fairly clean source. Also it only says NE555 on the ic, nothing more.
[QUOTE=DrLuke;33533812]I've powered it with USB, so it should be a fairly clean source.[/QUOTE]
This is a bad assumption. Digital devices are basically noise factories...
[QUOTE=ROBO_DONUT;33534256]This is a bad assumption. Digital devices are basically noise factories...[/QUOTE]
But it shouldn't be that bad, right? This square wave is running at roughly 1000 Hz.
PC power supplies contain a fair amount of high frequency common-mode noise which tends to be difficult to eliminate with plain RC lowpass filters, also
breadboards are prone to picking up and coupling noise as well, good layout and shielding can reduce this but not eliminate it.
Also your scope probe needs to be properly calibrated, you will get some overshoot regardless (particularly with fast signals) due to the limited bandwidth of your scope, a perfect square
wave with zero rise/fall time requires infinite bandwidth, this bandwidth is limited by your scope (input capacitance, sample rate, etc) and the circuit itself, by adding that 10uF capacitor
you increased the rise time of the the signal which in turn reduces the required bandwidth giving you smaller overshoot.
So that overshoot your seeing is either:
Caused by your scope due to improper calibration or lack of attenuation
Caused by the 555 timer
Or as is most likely, a bit of both.
Decoupling is important no matter how clean your input is.
Well, the guy who gave me the scope calibrated it right before he gave it to me.
[QUOTE=DrLuke;33536299]Well, the guy who gave me the scope calibrated it right before he gave it to me.[/QUOTE]
You need to check that the probe calibration trim pot is properly set, you can do this by using your test signal on your scope (if it has one) or a 1kHz square wave (you could use that 555 with a 100nF cap)
and adjust the trim pot until the edges look as clean as possible.
If your probe has an attenuation switch set it to 10x, this will reduce the capacitance and allow you to measure higher speed signals without problem, most scopes have their full bandwidth rating only on 10x.
Alternatively go buy a cheap 10x BNC attenuator.
[QUOTE=Chryseus;33536357]You need to check that the probe calibration trim pot is properly set, you can do this by using your test signal on your scope (if it has one) or a 1kHz square wave (you could use that 555 with a 100nF cap)
and adjust the trim pot until the edges look as clean as possible.
If your probe has an attenuation switch set it to 10x, this will reduce the capacitance and allow you to measure higher speed signals without problem, most scopes have their full bandwidth rating only on 10x.
Alternatively go buy a cheap 10x BNC attenuator.[/QUOTE]
Well, I've got a 1x probe and 10x probe, so I should better use the 10x probe?
[QUOTE=DrLuke;33536448]Well, I've got a 1x probe and 10x probe, so I should better use the 10x probe?[/QUOTE]
Always use the 10x unless you have a specific reason to do otherwise.
Progress on the oscilloscope! After checking the mains input a bit further the bridge rectifier appears to be shorted. Luckily some people on Ebay still sell replacements (It's a BY179), time to go shopping.
if I buy a wireless webcam, can I unsolder the transmitter bit and re solder it to a long piece of wire attached to the PCB in the right place ?
[url=http://www.falstad.com/circuit/#%24+1+5.0E-6+0.033846542510674225+45+5.0+43%0Av+224+368+224+96+0+0+40.0+5.0+0.0+0.0+0.5%0Al+224+96+304+96+0+0.01+0.15249806152952125%0Aw+304+96+368+96+0%0Ac+432+96+432+176+0+4.7E-4+9.248065349090508%0Aw+432+96+496+96+0%0Ad+368+176+368+96+1+0.805904783%0Ad+368+96+432+96+1+0.805904783%0At+272+144+304+144+0+1+-15.006958395961707+-5.0+100.0%0Aw+304+96+304+128+0%0Aw+304+160+304+176+0%0Aw+304+176+368+176+0%0Aw+368+176+432+176+0%0AR+272+144+176+144+0+2+4000.0+5.0+0.0+0.0+0.5%0Ar+496+96+496+160+0+100.0%0Aw+496+160+496+368+0%0Aw+496+368+224+368+0%0Ag+368+176+368+208+0%0Ag+224+368+224+400+0%0Ao+13+64+0+35+20.0+0.2+0+-1%0A]DC-DC-Converter[/url]
I'm gonna build it tomorrow!
I want to get one of the starting Parallax boards for Christmas.
How do I use a wireless webcam underwater then?
[QUOTE=Alcapwne;33547939]How do I use a wireless webcam underwater then?[/QUOTE]
Get that super-hydrophobic spray, coat wireless webcam with it
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