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So I went ahead and built an astable multivibrator from the 555. Works a charm! The tuning dial (all 4 caps now connected in parallel) gives me a nice square wave freq of around 1.8Khz-7.2Khz using 2.2k and 1M resistors. :)
Thanks for your help guys! I learnt a lot! :)
Cool I could do that. Or maybe using a 555 timer as I'm not sure I have a 74HC14 lying around? I guess I could build a schmitt trigger from opamps but using a 555 (which I have) may be easier
The capacitance would still be in the region of pFs I'd think right? (I dont have spec for my variable...
I'm still looking to build my Internet radio from this thing. I've got everything else working; software, volume control pot, audio out etc. just want a way to use the original tuning dial so I need to have it produce some sort of signal to feed my MCU so I can 'tune' channels (in an absolute...
Thanks for correcting me before I wasted time doing it! :) Makes sense I guess an inductive divider would work (dividing over resistive values). Don't know where I got the capacitive divider idea working for DC from; it'd just act like an open circuit after it's fully charged.
I should have...
I don't need existing tuning to work. Yeah I know that caps in DC won't conduct and therefore there will be no energy transfer. But I was under the impression that there would be a voltage drop across each one proportional to the ratio of their respective capacitances? So if I have C1 = 2uF and...
Yup I'm already using the potentiometer (on the voltage control). It works well.
I need to use the variable capacitor to the same effect (modify voltage over range for my ADC). SO I was thinking of connecting another cap in series with it, applying a voltage and thereby forming a voltage divider...
Hey guys
Thanks guys!
Yes; I believe it's a variable cap. Makes sense!
I'm ditching the AM/FM part and making a digital 'internet radio' from this. I wanted to make use of the original tuning dial to provide a variable voltage to and ADC connected to my MCU.
I guess using this as a capacitive...
So, I've been trying to modify an AM/FM radio and am having some issue with one of the potentiometers (or at least I've assumed it as such).
It's 4-pin by the looks of things and whoever I wire it up I cannot get any response from it. I've only really used 3-pin ones in the past and I always...
I've decided to leave off the drivers for now to leave my first attempt at a board generic. It has to externally interface with a bunch of other boards at the moment. The final design I'll put everything on one board and have more control.
Many thanks for all your help everyone!
I havent added the drivers yet but I've updated the power nets. Have I gone overkill?? (schematic attached).
I thought the ferrite beads should be high impedance (low-Q) for circuit isolation?
@FvM
Would a ferride bead on the VCCA_PLL be sufficient?
I guess I'd prefer to do away with the download cable header. The jtag indirect method doesn't require any special configuration on the fpga does it? It should work out-of-the-box with flash loader?
@shaiko
I'll bang some resistors ont he...
Thanks for all the help and advice.
I've pulled together a basic schematic together for the fpga board. Does this look right (my first attempt)?
Also first time using KiCad (usually I use Eagle) so sorry if things are weird...
Many thanks for all the helpful answers.
I guess I'll use a single-ended output with a termination resistor.
So I just connect this to CLK0 input pin of the fpga and leave the CLK pin NC?
I'm building my first FPGA circuit using an Altera EP1C3 and had a few questions regarding the oscillator:
1) I assume any oscillator frequency up to the rated max (200-something MHz) will work? I'm considering either 50- or 100 MHz (cost reasons and application doesn't need more)
2) The FPGA...
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