Recent content by Shafto

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    Tantalum vs Ceramic, Cap as short term "battery" power for PICAXE.

    Was messing around today, just being curious. I made a circuit where an 08M2 was powered by 3.5V, through a 10ohm resistor and diode, with a capacitor on the PICAXE side of the diode, so when power is removed, the capacitor charge keeps the PICAXE going for a couple of seconds. The PICAXE can...
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    Fan speed control chopper circuit

    Hello, I'm building the circuit seen here: https://www.youtube.com/watch?v=TF018JPytSg To control the speed of some 3 pin fans from the 4 pin headers on my computer motherboard. The circuit diagram has no output capacitor, but you can see it in the video, and it's mentioned in the comments...
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    Considerations for Picaxe running 24/7?

    I'm making a little LED display with a 28X2 chip that will be on all the time. 18 separate outputs from the 28X2 will turn on an N-channel MOSFET which will supply power to each of the 18 LEDs in a sequence, and a pot to adjust the pause time between switching to the next output. The current...
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    Which amplifier to use?

    I'm never sure if what I'm explaining will be clear or not, since I can see it so clearly myself. I tried. This schematic should do the trick though. This is how it's currently setup. The output from the temperature switch goes low when it overheats, so normally the input to the signal...
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    Which amplifier to use?

    I'm using the PWM output on the picaxe08M2 at 4.5khz flowing about 18mA. The PWM pin on the Picaxe goes to the source of a PNP FET and the drain to the load. The gate of the FET goes to a inverter that is connected to a temperature switch with an open drain output that is pulled up. When the...
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    Weird little problem.

    Having a very strange issue. I've narrowed it down the the PWMout command, but I can't figure out what's going on. With just a basic download circuit and an 08M2, using a PWMout C.2, 221, 500 command, the PWM output will work properly putting out 4500hz up to around a supply of 3.3V, above that...
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    OT: Jfet constant current source.

    I'm using a picaxe to control the sequencing of LED candles from the dollar store, but they aren't quite bright enough. I'd like to build some LED candles that run an LED at about 100mA as compared to the usual 20mA. I have some LEDs that can take 100mA and have a Vf of around 3V. My source...
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    Simple Picaxe LED driver.

    For running an LED off of a 3.7V nominal Li-Ion rechargeable battery (4.2V-2.7V) I have been using 0.12V drop 350mA Linear regulators in parallel combinations for differerent drive currents. I had an idea though, now that I've learned how FETs actually work from the switch that I made, to build...
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    Switching ground with a P channel FET?

    I thought this was possible, but maybe not, I seem to have myself confused now. I want to use a mechanical switch to energize a FET into conducting the negative side of an LED to the battery ground. I wired it so that the source is connected to -LED, drain connected to BAT GND, the gate with a...
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    Adjusting injected voltage bias for current feedback with Picaxe.

    Planning to control the brightness of a 1A LED from Off-1000mA using a hall effect sensor detecting the proximity of a magnet, running off a single 2.8-4.2v Li-Ion cell. Originally I planned to use the LTC3454 driver, for which I could easily use a DAC controlled by the picaxe to manipulate the...
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    Easy USB enumeration? Request 500mA draw

    I'm building a USB charger for a Li-Ion cell, and I'd like to be able to achieve 500mA from the USB port. From what I've read, I need to have a device that can be enumerated, and then request 500mA. I've seen a few USB to breadboard connectors with I/O pins and 100mA or 500mA draw, I'm just...
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    Serin from radar speed sensor.

    There's a bicycle race in town that a friend of mine is competing in, a fundraiser, and for my contribution I want to build something for the race. A radar speed sensor that will post the speeds on a 7 segment LED display down the straight stretch. The specs for the radar speed sensor that I...
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    PID solenoid air pressure control

    I've starting building a electronic control for a solenoid valve to control the wastegate actuator on my turbo charger, which diverts exhaust gasses around the turbine when open, lowering the manifold pressure, or "boost" as it's known. I know many cringe at the picaxe in the car situation, but...
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    Multiple output switch from momentary input.

    Building another LED driver for a flashlight that I made. Right now It's using one of these drivers: http://www.kaidomain.com/ProductDetails.aspx?ProductId=1801 3 AMC7135 chips, which are 350mA linear constant current regulators, and a control chip of some kind, I'm not exactly sure how it...
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    Simple Li-Ion monitor.

    I'm making an LED flashlight with 6 10440 size (AAA) cells. You can get many cells these days with protection circuits, unfortunately these smaller ones aren't available with onboard protection. I've already made a switching CC LED driver to run from 6 cells. I've also already built a Li-Ion...
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