tarsin hello, i am trying to build a circuit to control whether or not a device has power. the device is pretty low voltage.. around 6V. is a solid state relay a good application for this?
SpeedEvil No.
SpeedEvil They - most of them - work only at AC and high voltages
flyback that's not true
SpeedEvil what's the device - what are you trying to switch it with?
tarsin an atmel processor.... Arduino
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SpeedEvil flyback: yes, it actually is true. Go and look at the solid state relay of any catalog. Most of them will be triac and SSR based devices. These will _not_ work on DC.
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SpeedEvil flyback: and will have a volt or two of drop at operating current.
flyback uhh
flyback I seen both
SpeedEvil SCR based
SpeedEvil Sure - MOSFET based devices are available, They are much less common.
tarsin it has a few discrete outputs.. my idea was that i could set one of them high and then threw the magic of electronics the device would given power until i set that pin low again
SpeedEvil And IGBT - the remainder - are not suitable for use at low voltages.
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flyback oh I am sorry but WTF IS THIS
flyback http://www.google.com/search?hl=en&q=solid+state+relay+dc&btnG=Google+Search
SpeedEvil tarsin: what's the device you're switching? Does it draw much current?
SpeedEvil flyback: it's a google search URL
SpeedEvil I did not say they were unavailable. I said they were less common.
tarsin its a low voltage audio amplifier IC... its ran off 4 AA batteries.. the speaker is really small.. I can't imagine it draws much power but i dont have any numbers
SpeedEvil tarsin: Ok - you want to switch it from a PC or something?
tarsin i want to switch it from my Arduino board.. its a 16 bit atmel processor
SpeedEvil Where are you?
SpeedEvil US/...
tarsin yep california.
Strogg say.. how popular are the Arduino boards? are alot of people into them?
tarsin i've been hearing a lot about the lately.. they are kinda cool. pretty simple to program.. $34 a pop
SpeedEvil flyback: digikey - solid state relay - in stock. DC 55 items. AC 150 items
flyback i WOULD SAY 55 is not "ac only"
flyback nor is it rare
SpeedEvil I did not say rare.
SpeedEvil I said most.
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SpeedEvil Anyway.
SpeedEvil tarsin: does it matter if the ground of the arduino and the negative of the battery are connected?
SpeedEvil tarsin: does it matter if the ground of the arduino and the negative of the battery of the amplifier are connected?
flyback wow
flyback google is a joke anymore and they have ruined youtube also
tarsin i'm not really telling the whole story.. i am trying to hack my doorbell to play nintendo music.. i'd like to to be ran off batteries. the problem i am finding myself in is the programming environment arduino provides sits on a loop always executing. also drawing power from the battery is the ampifier curcuit.. so my concern is between those two the batteries will die quickly.. so i'd like a way to control power to both of them....
tarsin i hooked up a volt meter to my door bell, and found that when the doorbell button is pressed the loop is closed and electricity can flow. so what i'd like to do is, when the button is pressed both the Arduino and the sound amplifier are given power until the Arduino board sets one of its discrete outputs either high or low, signifying its done with its music player.. then everything turns off...
tarsin is that reasonable?
tarsin haha kind of a silly project but eh..
Strogg tarsin: it would be better to put the MCU to sleep, and have it wake when the button is pressed
tarsin SpeedEvil, i dont know the answer to that question.. i'm a software guy..
Adamant are LEDs for home lighting really overrated as room lights?
SpeedEvil Ok - fair enough. Can you when the arduino is powered on immediately play the music?
tarsin oh no it doesn't matter, because that is how i corrrently have it hooked up on my breadboard
tarsin currently*
SpeedEvil Adamant: in theory - they are up to it now.
SpeedEvil Adamant: in practice - not usually as sold
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Strogg ooh.. I just got one of those 1W luxeon flashlights yesterday.. man. they're cool :)
Strogg they are kickass bright.. I'm impressed
SpeedEvil Strogg: cree is cooler! (2* brighter)
Adamant SpeedEvil: so the newer versions that aren't everywhere yet are better than compact flourescent?
Strogg Adamant: it depends how you define "better"
SpeedEvil Adamant: they are - all things considered - usually about a wash.
Adamant well, use less power
Strogg they are longer lasting, lower power, etc, etc.. but they still cost more
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SpeedEvil Adamant: They are only lower power really if you consider only the _nastiest_ colour grades. Warm white is perhaps 30-50% dimmer.
Strogg I'm tempted to buy one of those 5W luxeons. hehe
Adamant yeah
SpeedEvil Adamant: lower power for watt that is
tarsin SpeedEvil, yes i can play music with the arduino. its just not loud enough for the purposes of a doorbell.. which is why i bought one of these http://www.biltek.tubitak.gov.tr/gelisim/elektronik/dosyalar/6/LM386.pdf
Adamant that sucks, I was hoping LED lighting would be even better than CF bulbs
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SpeedEvil tarsin: what I was meaning. Doorbell completes circuit, and turns on arduino and amplifier - it's simply a switch to the battery
Adamant thanks anyway people
Strogg LEDs are still quite directional too..
SpeedEvil Strogg: not really - there are common packages that'll do 140 degrees
tarsin it only completes the circuit as long as the buton is pressed.. so typically someone only holds the button for like a second.. as soon as the remove thier finger there the circuit is open
SpeedEvil tarsin: yup - you need now something wired across the switch, which can keep it powered.
SpeedEvil tarsin: and then remove that power on command
tarsin yeah
tarsin i just have no idea where to look for examples of how to do that
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Strogg get an amplifier than you can power down.. then just put the MCU to sleep and wait for a press
SpeedEvil tarsin: A solution is the P channel FET - like...
Strogg an AVR in sleep mode takes uA's
Strogg SpeedEvil: ooh.. you could use an SCR hehe
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halleck anyone around?
Strogg button turns on the SCR, it powers up the atmega which plys the tune.. when it is done the tune, it outputs a signal to a pin, which turns off a transistor breaking the SCR circuit. hehe
SpeedEvil Something like http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=2SJ412-ND
tarsin silicon-controlled rectifier?
SpeedEvil for example
SpeedEvil SCR won't work very well - 1.2V drop
SpeedEvil There are lots of alternatives.
SpeedEvil What the FET does - you connect the switch in the + supply. Now, wire the drain of the FET to the 'real' + supply, and the source to the switch. Now, as long as you keep the gate at '0' V, the FET will be turned on.
SpeedEvil And act like a .5 ohm resistor or so.
halleck I was wondering if someone had a good resource on hooking up motors to micro controllers etc. I have some nice h-bridges lying about but I have no clue how to wire in filtering capacitors etc. I googled for a bit but could not find a good resource. I just want a basic wiring diagram or something, maybe with some explanation of how/why it works.
tarsin hm interesting
tarsin ok cool thanks for the help
SpeedEvil So, you arrange it with a resistor to pull the gate high (1Mohm or so)
SpeedEvil then a small NPN transistor to pull it low on command. This is run from the arduino.
SpeedEvil So all you do is - power on - set an output high. This applies current through a resistor to the base of the NPN transistor, which turns it on.
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SpeedEvil This then conducts, and pulls the gate of teh FET low, turning it on and keeping the power on.
tarsin so i am wondering if i am going to run into some kind of debounce issue?? while the doorbell button being pushed is turning it on and off repeatedly? will this happen?
SpeedEvil Now, you play your tune.
SpeedEvil Nope.
tarsin sweet
SpeedEvil All you do when you want to power off is set the port low again
SpeedEvil the NPN transistor turns off, the 1M resistor discharges the gate, it goes off.
SpeedEvil (unless someones still holding the button)
SpeedEvil In which case it just turns off when they let go.
tarsin cool. tetris doorbell here i come!
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Triffid_Hunter halleck: you want a 10 to 100nF ceramic across the motor terminals, and one from each terminal to the case, all as physically close to the motor as possible
halleck ok, cool thanks
Triffid_Hunter halleck: you will also want diodes from the motor leads to your power source, so its inductive kick doesn't blow up your h-bridges. some h-bridges such as the L293D include these
halleck I am using L295 I don't believe it has those
Triffid_Hunter halleck: see http://www.kronosrobotics.com/an142/GAN142.shtml
halleck any specs on the diodes to use?
halleck ooh link :) thanks
Triffid_Hunter halleck: diodes should be fast if possible (shottky etc), and rated for the motor's stall current
Triffid_Hunter halleck: voltage rating should be about 1.5 * your supply voltage or more
halleck Triffid_Hunter: quick question what were your google terms to find that link? I could find nothing like it
halleck Triffid_Hunter: wow, ok thanks
Triffid_Hunter halleck: http://images.google.com.au/images?q=motor+suppression+capacitor 8th link
Triffid_Hunter lunchtime; bbl
halleck nice, well thanks again. I would not have known to reffer to it as noise supression
_gecko_senator_ what is better? optical stereo scope, or digital microscope for soldering
* uberpenguin likes stereo scopes
* Strogg so *hearts* optical stereo
halleck I personally prefer digital, but most people think I am crazy. It hurts my eyes looking in a optical scope for any length of time
Strogg it's mind blowing. :)
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_gecko_senator_ yeah, it gives me a headache
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_gecko_senator_ but you can see in 3d
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_gecko_senator_ what if I have 2 digital microscopes, and two monitors, then just parallelize my eyes
Strogg it gave me a headache until I figured out to stop fighting the 3d effect.. then it just seemed natural
_gecko_senator_ so left eye is on the left monitor right on the right monitor.. then I would still see 3d
Strogg _gecko_senator_: if you can do that with the scope, then you're all set.. just change your eye focus until you get the right focus distance..
Strogg everything just snaps into 3d and it's so awesome. hehe
_gecko_senator_ yeah
_gecko_senator_ I can do it, but the monitors need to be 5 feet away or so
_gecko_senator_ which is ok
_gecko_senator_ but it also means I have to buy two digital microscopes
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* Strogg wants to get an 15-20X stereo optical scope
Tom_L on an ATTINY13, how fast I can switch the pwm outputs into being an analog comparitor input and back to pwm?
_gecko_senator_ well, you can run the pwm output at the clock frequency right?\
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_gecko_senator_ it depends on what bandwidth you need
Tom_L just driving a couple motors
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_gecko_senator_ uh
_gecko_senator_ so I found a potential stereo digital microscope
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flyback does the vrm section for the cpu on a mb normally run hot
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Strogg only if the caps are messed up
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