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  1. S

    Increase common mode range of INAMP??

    Hi, Just wondering if anyone knows of a nice little circuit to decrease the common mode voltage at the input to a differential instrumentation amp? I'm using the AD8555, currently working ok with a common DC level of up to about 6V. Problem is I need to measure power consumption etc on a 12V...
  2. S

    Digital trace over analog ground region

    Hi, I have a question regarding a mixed signal PCB design. I have a board with partitioned ground planes (AGND and DGND) but there is an analog IC that requires a digital control signal from the CPU that cannot be physically positioned on or near the analog/digital border. So basically I have...
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    Lithium Thynol Chloride battery issues

    thynol Hi All, Not sure if I'm in the right part of the board here... I was wondering if any of you have experience with Lithium Thynol Chloride cells? I'm having endless dramas with reliability, possibly due to passivation. I am preconditioning the cells according to the datasheet (Tekcell...
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    Controlled impedance routing in Altium Designer

    routing corners Thanks for the reply. I still cant seem to get this rule working though... Here's a more detailed description of the steps Ive taken. I have placed a ground plane on the bottom layer, and an adjacent plane on the top layer. I used place>polygon pour, and connected them both to...
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    Controlled impedance routing in Altium Designer

    controlled impedance calculator no ground plane Hi, I'm wanting to tune the impedance of some tracks in a layout that is already complete. I have tried turning on 'characteristic impedance driven width' in routing rules, but no matter which parameters I change here or in the layer stack...
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    Parallel RLC circuit conversion

    Thanks for the replies. I think i've got it sorted.. I found the admittance of the parallel circuit, then simply found the related impedance Z=1/Y, then as far as i can tell, the real component of this impedance is my series resistance for the series equivalent. What do you think? Anyway, we...
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    Parallel RLC circuit conversion

    Hi, I need to convert a high frequency inductor model from a parallel RLC circuit (all three elements in parallel) to a series RL in parallel with a capacitor. I know the resonant frequency will be the same, so for a given inductance the capacitance will be the same, but i'm guessing the...
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    Rounded corners in Protel???

    Hi, I want to route a pcb with rounded corners in Altium Designer 6 (new version of protel) and i cant seem to find any way to do it apart from using arcs... I have tried selecting 'rounded' in the corner section of the design rules, but it does nothing. This is driving me crazy!! Any ideas...
  9. S

    Any Induction Loop Geeks?

    Hi, If i was to play a guitar, take the output signal, then feed it back into the pickups via and induction loop system what would happen? I'm thinking there will probably be a huge amount of nasty feedback, but could this be tamed to provide sustain or controlled feedback? I mean, could the...
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    Identifying old transformer

    Ok, ill try to hack into it (stripped screw holding me back) and see if i can figure out which is the primary. I still dont get what you mean by the 4 wire thing... Once i figure out which side is the primary, how do i connect the 4 wires to mains?? Thanks, Sam
  11. S

    Identifying old transformer

    Hi, I bought an old transformer at a garage sale a while ago and was wondering if you guys might be able to help me figure out what it is. It is pretty big, about 15x15cm. The only markings are... 10-1222-A NTK 230454 On one side there are 2 blue wires and 2 grey. On the other side there...
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    LOHET1 current sensor problem

    Hi, I'm using a hall effect current sensor IC mounted in a current transformer to measure AC current via a micro. It is supposed to output an AC voltage proportional to the AC current sensed. This is all working fine, but i noticed something quite strange... The output waveform is exactly...
  13. S

    Solution to oscillating preamp issue

    Hi, I've built a guitar amp using the schematics on this site **broken link removed** It is mostly working fine, but when i flick the 'bright' switch, the opamp goes into oscillation. I've bypassed both power pins to ground with 0.1uF ceramics, and I've tried it with the power amp...
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    Low frequency oscillation problem in opamp

    Re: oscillating opamp Thanks everyone for the advice. It turned out to be coming from the virtual ground. I stuck a 0.1uF cap from earth to virtual ground, and a 56pF cap across the 22k feedback resistor, and now it is working perfectly. Opamps are much simpler on paper.. Thanks again, Sam
  15. S

    Low frequency oscillation problem in opamp

    Re: oscillating opamp Yep, I've got the input biased at 4.5V. It's a 9V battery supply, with 2x680k resistors dividing it for the input. I have used a seperate 4.5V bias for the feedback virtual ground. I spoke to one of my lecturers and he suggested sticking a small cap from the virtual...
  16. S

    Low frequency oscillation problem in opamp

    Hi, I've modified a guitar pedal design to include a gain stage at the output. There was already an opamp buffer at the output, so i've just converted it to a single supply (9V) non-inverting amp. I've learnt the theory of opamp circuits at uni, but we've never really played around with them...
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    Mains voltage metering issues

    Re: Mains Metering Issues The input on the primary is definetely sinusoidal (240V AUS mains). The waveform on the secondary isn't completely triangular either, it's something in between sin and trangle.. I'm pretty sure it's a normal transformer. 2x6V secondaries .35VA made by a german...
  18. S

    Mains voltage metering issues

    Re: Mains Metering Issues My probe is a 10X. Why do you need a special probe for this kind of signal? I'm far from up to scratch on transformer theory... The transformer i'm using has 2 secondary windings, 2x6V. I'll try sticking the cap in line with the probes earth lead. thanks a lot...
  19. S

    Mains voltage metering issues

    Re: Mains Metering Issues thanks for the reply. I tried it with the 100ohm resistor, and it is pretty much exactly the same shape. it helps a little bit, but it definetely doesn't make it a sine wave. how does adding the resistive load change the wave shape? any other suggestions would be...
  20. S

    Mains voltage metering issues

    Hi, I'm working on a final year project with the aim of remotely metering mains voltages and currents in a 3-phase distrobution box. here's our setup.. step down voltages with .35VA 6V transformers, apply 2.5V offset, take 64 samples per 20ms (for 50Hz) via the ADC in an AVR ATmega16 micro...

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