microcontrollers anyone?

[klims]

hey guys. i know this is not an rc question, but you guys seem to know a fair bit about electronics and so who better to ask. i am using a microcontroller to drive a relay. it uses the digital out from the microcontroler to fire off a transistor which in turn closes a circuit so that the relay can be activated. i found a wiring diagram from a book that shows how this can be done using the serial ports from a pc. my question is that the circuit has been tested and works when applying 5v @ 1mA from a battery pack, however when using the exact wiring as shown in the picture it does not work. my explanation is that there is no complete circuit from the microcontroller to the transistor, just a 5V (high). oh and the arrows in the picture dont point in the direction of current flow. they seem to be there to show where the wires should be going. thanks guys[ATTACH]165[/ATTACH]

[klims]

i should probably also mention that the digital out from the microcontroller is only 4v.

[merc-blue]

you sure you got the wires to the right places on you prototype that circuit looks pretty good at a glance 4V out should still be enought to open the Transistors furthenough to switch the realays, ill look at tha data sheets this arvo to see if thats right, odds are its a silly thing like a reverse polarised diode or somthing? if your 100% sure it all good check voltages after R1 R3 R5 R7 and if there below they switching voltage then tear out R1 R3 R5 R7 and see if that helps but once again will have to look at the data sheet

also there are better cicuits to use, microcontrollers are much better sinking than sourcing might look into that?

[klims]

yeah everything works perfectly. i have tried it with a 5v from the battery, but that was grounded to the same source. i will try firing it off with 4v and see what happens. i’m convinced that it is because the high from the microcontroller has no complete circuit, but apparently thats not an issue. i will try all those things merc and come back with a result. thanks for the help

[klims]

hey thanks for all the help merc. turns our 4v is enough to drive this puppy and i missunderstood what someone was telling me, which meant that i didnt hook the – terminal up to the microcontroller. IDIOT!

[merc-blue]

lol, dont worry mate its been done before, i forgot a ground when making a 8 bit updown decade counter out of just bottom level gates, ahhh there goes 3 hours of time silly patch boards,

no prob for the help, even though i didnt acctually help, could we inquire about what the project is?

[klims]

yeah definately. its for a 3rd year engineering project taking place right across the country. the local competition takes place at swinburne uni this friday, with the winners going on to compete in sydney against the rest of australia. should be fun. i hope to post some pics of our beast and maybe some competition video as of friday.

[klims]

hey guys. sorry its taken me so long to get some pictures. i gave up and ended up getting the ones from my phone. i have some vids too but not sure how to post them. its not the prettiest beast in the world, but it worked… not very well but it worked.

[klims]

turns out there were some offices that were completed but the lecturers hadnt moved in yet, so we hijacked one and set up shop.

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