Transformer Question - Page 1
Forum section: electronics / beginners

author: ASHU
author_rank: Contributor
timestamp: July 04, 2015, 05:49:44 pm
content: Hi,I am new to electronics and was trying to make something( shown in the picture attached). I know there are things like capacitors and resistors, etc missing in the diagram, so sorry about that.My question is I have two or more different switches feeding power to the transformer, so is their any way through which i can know as to which switch was turned on or rather more specific as to which line is providing power to my transformer.I their something which I can add to my circuit to know that, so my 74HC165 register can read as to which swithc is on/off

author: Hideki
author_rank: Frequent Contributor
timestamp: July 04, 2015, 06:16:07 pm
content: It's a strange question. Current needs to run in a loop to do anything useful, so both switches need to be turned on to power the transformer.(Unless you plan use the ground connection as the return path? Very bad idea.)

author: Cliff Matthews
author_rank: Unknown
timestamp: July 04, 2015, 06:32:29 pm
content: Yes, power needs a return path. But the fact the 74HC165 will work at allISbecause the regulator is getting power, so why?

author: ASHU
author_rank: Contributor
timestamp: July 04, 2015, 07:26:50 pm
content: Basically I just want to know the state of the 5 different switch (on or off) so that i can send it back to my micro-controller (as 1 or 0) so how do i do it? If i connect everything to the transformer then even if a single switch is on, it will tell me than all switches are on. how do i divide them? Or do i need to use different transformer for different switches?

author: IanB
author_rank: Super Contributor
timestamp: July 04, 2015, 07:36:00 pm
content: Maybe you can tell us what you are trying to do with this arrangement? Instead of asking for a technical answer to what may be the wrong question, tell us instead what problem you are trying to solve. Then someone might be able to tell you the best way to solve that problem.

author: xxngo
author_rank: Contributor
timestamp: July 04, 2015, 07:55:26 pm
content: Im have a hard time understanding the question. first of all why do you need more than one switch from the same source to the same transformer. I'm new to electronic as well so maybe its my lack of knowledge. or maybe the transformer have more than one primary input, but then again the switches are connected to a single source......ahhhhhhh my head hurts WTF.....

author: ASHU
author_rank: Contributor
timestamp: July 04, 2015, 08:17:30 pm
content: I'am connecting transformer in parallel to loadI want to know the state of the switch on/off. So that i can display on my webpage if a light/ any other component is on or off. I am able to do that with led as it's low voltage dc. I am using 75hc165( parallel in serial out shift register to know if the led is on or off). If the circuit is complete it will provide 1 as output else 0I want to do same with the mains power (220VAC) but then I need to reduce the voltage as it will destroy my 74hc165 shift register. So for eg: I want to know the status of a single switch. I can reduce the voltage through the transformer then use a full bridge rectifier and capacitor to get a static dc 5v which the shift register can read.Now i want to do the same with let's say 2 switches. So to connect them both to the shift register. I need to reduce power for both the switch, so i connect then both in parallel to a single transformer but after the transformer reduces the voltage the path becomes common. so I don't come to know if switch one was turned on or switch two.So i wanted to know what can i do/add to my circuit so that i can know if it was switch one or switch two which was turned on.

author: electronics man
author_rank: Frequent Contributor
timestamp: July 04, 2015, 08:52:03 pm
content: Quote from: ASHU on July 04, 2015, 08:17:30 pmso are you not actually powering anything with your transformer? whats the point?

author: xxngo
author_rank: Contributor
timestamp: July 04, 2015, 09:13:19 pm
content: I'm sorry but I dont think I really get what you're trying to do.sounds to me like you want to parallel 5Vdc to 3 different branch, correct me if im wrong. If thats the case then you dont need that many switch. looking at the circuit, to my limited understanding. all you need is one switch to turn the transformer on, after that you already have the bridge and filter follow by the 7805 whichh output 5Vdc. Then why dont you just parallel that 5V to your branches. one branch goes to your shift register and whatever needs the 5V just parrallel it off there.or am I not getting what you're trying to do....

author: IanB
author_rank: Super Contributor
timestamp: July 04, 2015, 10:35:03 pm
content: OK, let me try to translate.You have various mains powered devices around the house, like lamps for example. You want to detect if they are switched on (when you are away?) and you want to show this on a web page so you can see it remotely?

author: ASHU
author_rank: Contributor
timestamp: July 05, 2015, 04:42:37 am
content: Yes IanB thats what i,am trying to doXxngo: no that's not the caseElectronics man: yes you are right, i am not powering anything with transformer, i'am just using it to so that i get a constant 5v dv for my register, sorry but I don't know what else to use, I have seen videos about how to make your circuit with transformer, but i have no idea if they provide constant supply or not

author: ASHU
author_rank: Contributor
timestamp: July 05, 2015, 04:50:33 am
content: Basically i just need a electricity sensor which can handle 220-240vACAnd can send signal to my micro controller if current is flowings through it or not

author: Hideki
author_rank: Frequent Contributor
timestamp: July 05, 2015, 08:51:19 am
content: Quote"Why didn't you just say so in the first place?"With minimal parts, you could perhaps use something like the HCPL3700.Another alternative is to build it yourself -- perhaps similar tohttp://circuit-electronic-models.blogspot.com/2012/09/mains-voltage-detector.htmlYou probably don't need the fuse, and could probably get away without using a full diode bridge.

author: ASHU
author_rank: Contributor
timestamp: July 05, 2015, 10:16:18 am
content: woowww....that's actually what I wantedthanks a lot hideki....you are Geniusfrankly,I wasn't aware if some thing like this even existed.so now I can directly supply 220vAC to the HCPL3700 and it will provide a constant 5vDC (if the mains power is on). right?

author: Hideki
author_rank: Frequent Contributor
timestamp: July 05, 2015, 10:39:42 am
content: It will not provide 5V because it's only a transistor switch. You get the 5V from the same supply that powers your shift register.

author: ASHU
author_rank: Contributor
timestamp: July 05, 2015, 11:16:10 am
content: ok, sorry for bothering you againI need to use one HCPL3700 with every switch? or I can even know the switch number through some other IC operational on mains?also what will be the output? between -0.5 to 20 v only? (as per the datasheet)

author: Hideki
author_rank: Frequent Contributor
timestamp: July 05, 2015, 01:01:28 pm
content: Unless you provide a proper drawing of what you want to do, there is no way for anyone else to say if you need one per switch -- but most likely, you do.As I tried to explain in the previous post, there is no voltage output, only an only a transistor with an open collector that turns on whenever the input voltage is above or below a certain threshold.You need to supply the chip with ground and 5V (it can handle up to 20V). You also need a pullup resistor from the output (Vo) to 5V that makes the output stay high (logic "1") when the transistor is off. Once it turns on, the output will be grounded, and you get a low voltage (logic "0").Now, the actual output of the HCPL3700 will rapidly turn on and off as the AC waveform goes through zero. If you are not prepared to handle that, you can either smooth it out with a rectifier and capacitor on the output, or use the other circuit which already has a capacitor on the input that should make the LED continue to work for the brief moment when there is a zero crossing.

author: ASHU
author_rank: Contributor
timestamp: July 05, 2015, 01:28:52 pm
content: OookayyyThanks a lot for the help

author: xxngo
author_rank: Contributor
timestamp: July 06, 2015, 04:24:49 am
content: ohhhhh i get it now. shit im slowpoke O0 sorry bout that. but yah great to know that u found your solutions.

author: tron9000
author_rank: Frequent Contributor
timestamp: July 06, 2015, 11:02:31 am
content: Quote from: ASHU on July 05, 2015, 10:16:18 amwhatever you can think of, there's most likely a chip for it!Just google "<insert application> IC".