Another electronics blurb by vthiru!

vthiru · 18th July 2001, 2:55 AM

OK,
for some reason i woke up this morning with an urge to have another crack at my PC-Powerup project. I soldered an IN4004 rectifier diode (reverse biased) across the 12V supplied by the PC, at the plug i made where it is passed out of the case.

Ive re-checked all the voltages like before, checked for open circuits and all, all seems well. There is none of that "600V" i registered once before.

Question 1
Can holding the DMM probes a bit shakily cause you to get voltage readings in excess of the signal voltage? Like when the probe tips touch/disconnect, the reading jumps before it falls, sometimes exceeding the 600V range of the DMM.

Question 2
Also something wierd (?) my DMM measures less than 1V (0.9 or 0.09V i forget) between the Neutral and Live wires - at the socket, anywhere... same reading (or little less) between live and my body... Is this normal? I presume it is... I have never noticed this before... maybe humidity has something to do with it?

Anyway, the resistance across the relay contacts is 0 ohms, so i dont think the "carbon deposit caused by arcing theory" is true... So the modified (+diode) version is working OK so far... But i know i cant draw conclusions, it may stop working after 3 days. Lets wait and see...

vthiru

Thanks for your guidance people!!

vthiru · 18th July 2001, 2:58 AM

Oh btw, someone recommended an IN4001 diode, i didnt have any at hand so i used IN4004 - is that alright? Its rated 400V 1A (seems right to me).

vthiru

Audiobuzz · 18th July 2001, 11:02 AM

Without seeing your DMM it's hard to say whats causing the 0.9v reading on the live-neutral lines. Are you sure you have set up the DMM properly. What sort is it?

some DMM's have a seperate plug for the lead for when you are measuring high voltages. is is digital or analogue. if it's digital then if you have it set on DC rather than AC, you will only be reading the average voltage which will be near zero. you will get the same for an analogue meter but you may be able to see the needle jitter a bit.

so basically, you should be reading 240Vrms if you have your DMM set up correctly and you are reading from the correct points.

vthiru · 18th July 2001, 11:48 AM

Yeah the DMM is digital (Digital MultiMeter) but i also have an analogue meter. I am sure i use the 600VAC range on the DMM and the 400VAC range on the analogue meter... With the analogue... its even wierder... that residual voltage - the needle deflection is roughly constant at ALL of the AC voltage ranges (bout half a cm to one cm)... wtf?

Oh and another thing... is it normal for the DMM to make a soft click (like a quiet relay) when the probes first come into contact with the 240V ? It measures the voltages alright (239 - 240 V).

vthiru

Audiobuzz · 18th July 2001, 12:14 PM

Yeah ok I'm awake now (DMM = digital m...., doh!!) :-)

I'm a bit confused though. you said it measures voltages ok.
"...rst come into contact with the 240V ? It measures the voltages alright (239 - 240 V). ...)

so what is it that it is not measuring correctly?

vthiru · 18th July 2001, 12:56 PM

Ummm..... AB, i think its all there.... no point repeating......? Thanks!

vthiru

vthiru · 19th July 2001, 8:45 PM

)*#&+$*@^_*%(^@! %*^!^()@*#()*#!+@&$*)(@^~_($

DAMN!

Its day 3 again and my relay project stuffs up again!!

The monitor makes some sort of continous sparking noises (or maybe a relay clicking repeatedly?) and then switches off.

Is there something im missing here? I'm already using the diode across the relay......

Maybe its the monitor?? Maybe the monitor's not supposed to be turned on other than by its own power switch...... but when i plug it into the mains while its switched on, in powers up fine....

WTF?!?!?!?!?

Stupid (#$*@&*^(!@#(*&_^# P.O.S. ){({+(*&#@+*$^@^$@)

Is the relay or monitor doing something sinister that i dont know..?!

AAAAAAAAARRGHHHH!!!!!!!!!!!!

vthiru

Widowmaker · 20th July 2001, 12:29 AM

vthiru mate if there is noises like that and it aint working i wouldnt play withit much more , you should be able to swith the power if the monitor without such noises i will grab some stuff at jaycar tomorrow and see if i get the same results

vthiru · 20th July 2001, 2:52 PM

Yeah ive pretty much had it with this... you cant always get what you want

Please do keep us informed about ur progress,

vthiru

Odje · 21st July 2001, 11:56 PM

the IN4001 or the IN4004 will work fine

is there enough voltage to pull the relay in

i have noticed with most computer powersupplies don't provide 12V. out of all the ones i have measured, i got 10-11.5V

when i was testting a relay with a battery, it did had enough power to pull in the relay then it would drop out, then it would pull in again and the that repeated

then i tried it with a transformer, so i assumed that there was not enough power to keep the relay in.

bout ur dmm and the netual wire measuring 0.9v, i noticed something like that a couple of days ago

i was installing some light fittings

i was not bothered to go turn the whole circuit of and it was night time so then it would all dark and i would not be able to see what i was doing

the switch on the wall was off and just to make sure i got my dmm out to see if there was any voltage and i got a reading of little above 3V AC

i thought it was my dmm screwing up

i thought you might want to add that to your collection of weird things

vthiru · 22nd July 2001, 2:21 PM

Yes odje, in fact i do get about 11.5 - 11.7 V from my computer... i only have a 200W PSU, i dunno if thats the cause, but ive never had any power-related problems... **

About the relay, it always switches properly... I think theres some wierd feedback between the monitor/speakers and the relay... maybe inductance/capacitance somewhere... Heck, maybe the problem with the "buzzing" from the Jaycar kit was caused by the same thing...

Hmm... i too scared now to try anything further, those clicking (sparking??) noises from my monitor... sheesh... no monitor -> me=vegetable until i get a new monitor...

I cant understand it... Oh well at least my blue LED and switch controlling my case fan has worked since i installed it a few months ago... And at least I now have a 12V socket at the back of my PC...

** Actually..... now i remember that i could not power my LCD display visibly enough from "stealing" power from my parallel port... but thats not meant to supply more than a few milliamps, even though it is 5V, although some circuits i have come across on the web say it should work fine.... had to use 5V from a battery... and it didnt even have a backlight...

stranger and stranger.......

vthiru

Odje · 22nd July 2001, 10:33 PM

the weirrd and wonderful world of electronics

and i too become a vegtable when i can't use my computer

i either got to sleep or i actually get my homwork done

mmmm....... i like sleep

18th July 2001, 2:55 AM	#1
vthiru Member Join Date: Jun 2001 Location: Bathurst, NSW Posts: 934	Another electronics blurb by vthiru! OK, for some reason i woke up this morning with an urge to have another crack at my PC-Powerup project. I soldered an IN4004 rectifier diode (reverse biased) across the 12V supplied by the PC, at the plug i made where it is passed out of the case. Ive re-checked all the voltages like before, checked for open circuits and all, all seems well. There is none of that "600V" i registered once before. Question 1 Can holding the DMM probes a bit shakily cause you to get voltage readings in excess of the signal voltage? Like when the probe tips touch/disconnect, the reading jumps before it falls, sometimes exceeding the 600V range of the DMM. Question 2 Also something wierd (?) my DMM measures less than 1V (0.9 or 0.09V i forget) between the Neutral and Live wires - at the socket, anywhere... same reading (or little less) between live and my body... Is this normal? I presume it is... I have never noticed this before... maybe humidity has something to do with it? Anyway, the resistance across the relay contacts is 0 ohms, so i dont think the "carbon deposit caused by arcing theory" is true... So the modified (+diode) version is working OK so far... But i know i cant draw conclusions, it may stop working after 3 days. Lets wait and see... vthiru Thanks for your guidance people!!

18th July 2001, 11:02 AM	#3
Audiobuzz Member Join Date: Jun 2001 Location: Adelaide Posts: 954	DMM Without seeing your DMM it's hard to say whats causing the 0.9v reading on the live-neutral lines. Are you sure you have set up the DMM properly. What sort is it? some DMM's have a seperate plug for the lead for when you are measuring high voltages. is is digital or analogue. if it's digital then if you have it set on DC rather than AC, you will only be reading the average voltage which will be near zero. you will get the same for an analogue meter but you may be able to see the needle jitter a bit. so basically, you should be reading 240Vrms if you have your DMM set up correctly and you are reading from the correct points.

21st July 2001, 11:56 PM	#10
Odje Member Join Date: Jun 2001 Location: Sydney Posts: 2,277	the IN4001 or the IN4004 will work fine is there enough voltage to pull the relay in i have noticed with most computer powersupplies don't provide 12V. out of all the ones i have measured, i got 10-11.5V when i was testting a relay with a battery, it did had enough power to pull in the relay then it would drop out, then it would pull in again and the that repeated then i tried it with a transformer, so i assumed that there was not enough power to keep the relay in. bout ur dmm and the netual wire measuring 0.9v, i noticed something like that a couple of days ago i was installing some light fittings i was not bothered to go turn the whole circuit of and it was night time so then it would all dark and i would not be able to see what i was doing the switch on the wall was off and just to make sure i got my dmm out to see if there was any voltage and i got a reading of little above 3V AC i thought it was my dmm screwing up i thought you might want to add that to your collection of weird things __________________ FOR SALE: unRAID Server Pro Registration Key $75 There are only 2 reasons why you should run, 1. If you are being chased or 2. If you are on fire

22nd July 2001, 10:33 PM	#12
Odje Member Join Date: Jun 2001 Location: Sydney Posts: 2,277	the weirrd and wonderful world of electronics and i too become a vegtable when i can't use my computer i either got to sleep or i actually get my homwork done mmmm....... i like sleep __________________ FOR SALE: unRAID Server Pro Registration Key $75 There are only 2 reasons why you should run, 1. If you are being chased or 2. If you are on fire

18th July 2001, 2:58 AM	#2
vthiru Member Join Date: Jun 2001 Location: Bathurst, NSW Posts: 934	Oh btw, someone recommended an IN4001 diode, i didnt have any at hand so i used IN4004 - is that alright? Its rated 400V 1A (seems right to me). vthiru

18th July 2001, 11:48 AM	#4
vthiru Member Join Date: Jun 2001 Location: Bathurst, NSW Posts: 934	Yeah the DMM is digital (Digital MultiMeter) but i also have an analogue meter. I am sure i use the 600VAC range on the DMM and the 400VAC range on the analogue meter... With the analogue... its even wierder... that residual voltage - the needle deflection is roughly constant at ALL of the AC voltage ranges (bout half a cm to one cm)... wtf? Oh and another thing... is it normal for the DMM to make a soft click (like a quiet relay) when the probes first come into contact with the 240V ? It measures the voltages alright (239 - 240 V). vthiru

18th July 2001, 12:14 PM	#5
Audiobuzz Member Join Date: Jun 2001 Location: Adelaide Posts: 954	Yeah ok I'm awake now (DMM = digital m...., doh!!) :-) I'm a bit confused though. you said it measures voltages ok. "...rst come into contact with the 240V ? It measures the voltages alright (239 - 240 V). ...) so what is it that it is not measuring correctly?

18th July 2001, 12:56 PM	#6
vthiru Member Join Date: Jun 2001 Location: Bathurst, NSW Posts: 934	Ummm..... AB, i think its all there.... no point repeating......? Thanks! vthiru

19th July 2001, 8:45 PM	#7
vthiru Member Join Date: Jun 2001 Location: Bathurst, NSW Posts: 934	)#&+$@^_%(^@! %^!^()@#()#!+@&$)(@^~_($ DAMN! Its day 3 again and my relay project stuffs up again!! The monitor makes some sort of continous sparking noises (or maybe a relay clicking repeatedly?) and then switches off. Is there something im missing here? I'm already using the diode across the relay...... Maybe its the monitor?? Maybe the monitor's not supposed to be turned on other than by its own power switch...... but when i plug it into the mains while its switched on, in powers up fine.... WTF?!?!?!?!? Stupid (#$@&^(!@#(&_^# P.O.S. ){({+(&#@+$^@^$@) Is the relay or monitor doing something sinister that i dont know..?! AAAAAAAAARRGHHHH!!!!!!!!!!!! vthiru

20th July 2001, 12:29 AM	#8
Widowmaker Member Join Date: Jun 2001 Posts: 2,219	vthiru mate if there is noises like that and it aint working i wouldnt play withit much more , you should be able to swith the power if the monitor without such noises i will grab some stuff at jaycar tomorrow and see if i get the same results

20th July 2001, 2:52 PM	#9
vthiru Member Join Date: Jun 2001 Location: Bathurst, NSW Posts: 934	Yeah ive pretty much had it with this... you cant always get what you want Please do keep us informed about ur progress, vthiru

22nd July 2001, 2:21 PM	#11
vthiru Member Join Date: Jun 2001 Location: Bathurst, NSW Posts: 934	Yes odje, in fact i do get about 11.5 - 11.7 V from my computer... i only have a 200W PSU, i dunno if thats the cause, but ive never had any power-related problems... About the relay, it always switches properly... I think theres some wierd feedback between the monitor/speakers and the relay... maybe inductance/capacitance somewhere... Heck, maybe the problem with the "buzzing" from the Jaycar kit was caused by the same thing... Hmm... i too scared now to try anything further, those clicking (sparking??) noises from my monitor... sheesh... no monitor -> me=vegetable until i get a new monitor... I cant understand it... Oh well at least my blue LED and switch controlling my case fan has worked since i installed it a few months ago... And at least I now have a 12V socket at the back of my PC... Actually..... now i remember that i could not power my LCD display visibly enough from "stealing" power from my parallel port... but thats not meant to supply more than a few milliamps, even though it is 5V, although some circuits i have come across on the web say it should work fine.... had to use 5V from a battery... and it didnt even have a backlight... stranger and stranger....... vthiru