Bring 110 volt to 90 volt

[douglassanford]

I have a problem at a High school I just started here and the cubicals that the students work in have 115 volts. I was thinking of putting the feeds in series through incandescent bulbs. Have not tried this yet. Is there any other way. I will also use GFCI's. Thank you.:

 

[dereckbc]

OK why would you want to drop the voltage to 90 volts?

 

[iceworm]

25V buck boost transformer

doug - In all due respect, there is not one of us that has a clue what you are trying to do.

ice

 

[Ohms law]

Purple unicorns? I don't understand.

 

[douglassanford]

I have a problem at a High school I just started here and the cubicals that the students work in have 115 volts. I was thinking of putting the feeds in series through incandescent bulbs. Have not tried this yet. Is there any other way. I will also use GFCI's. Thank you.:

I am trying to keep the voltage down so the students are safe.

 

[iceworm]

I am trying to keep the voltage down so the students are safe.

Okay - that's always a good idea.

What is the circuit used for?

Is this 115VAC?

Is it going to a standard receptacle?

If not, what does it go to in the cubicle?

ice

 

[texie]

I am trying to keep the voltage down so the students are safe.

Huh? You think this will make the students safe? I don't think so.

 

[Besoeker]

Huh? You think this will make the students safe? I don't think so.

I agree. SELV rules.

 

[Ohms law]

I am trying to keep the voltage down so the students are safe.

Safe from what? Can you explain from A to Z what you are doing?

 

[douglassanford]

It's 110vac thanks . And what's with the negative comments from the others.
I'm trying to keep contact voltage down when testing there projects . Try thinking from A to Z.
I thought this site had class. Those of you that are bothered by question don't reply.
I ask for help , guess not everyone knows everything you gentleman know. So one more time. Students , voltage , safely.

 

[Besoeker]

It's 110vac thanks . And what's with the negative comments from the others.
I'm trying to keep contact voltage down when testing there projects . Try thinking from A to Z.
I thought this site had class. Those of you that are bothered by question don't reply.
I ask for help , guess not everyone knows everything you gentleman know. So one more time. Students , voltage , safely.

Not sure what you want but 90V isn't safe.

 

[Fulthrotl]

It's 110vac thanks . And what's with the negative comments from the others.
I'm trying to keep contact voltage down when testing there projects . Try thinking from A to Z.
I thought this site had class. Those of you that are bothered by question don't reply.
I ask for help , guess not everyone knows everything you gentleman know. So one more time. Students , voltage , safely.

please. may i have another cup of graciousness?

"Students , voltage , safely...."

got it.. it's a complete the sentence riddle.....

"Students , voltage , safely..... idiot."

25 volts can be a lethal voltage.
i suggest you drop the voltage to 12 volts, and
current limit it to 25 milliamps.

that should help. stay safe.

btw, the site has class. i don't. but you probably got that.

 

[nicholaaaas]

It's 110vac thanks . And what's with the negative comments from the others.
I'm trying to keep contact voltage down when testing there projects . Try thinking from A to Z.
I thought this site had class. Those of you that are bothered by question don't reply.
I ask for help , guess not everyone knows everything you gentleman know. So one more time. Students , voltage , safely.

Explain how this is safer. Can't wait to hear

Sent from my SM-T217S using Tapatalk

 

[GoldDigger]

If you really want to do something to increase safety, make sure that you have good GFCI protection.
And if there are no static sensitive parts consider isolating the students from ground.
1. Do you think that some of the products they will be working with are poorly enough designed that powering them with 120V is going to overstress them and cause them to fail?
2. Are you worried about spark/arc or electrocution? Series light bulbs could certainly act as current limiters, although probably not sanctioned formally.

Sent from my XT1080 using Tapatalk

 

[fmtjfw]

I have a problem at a High school I just started here and the cubicals that the students work in have 115 volts. I was thinking of putting the feeds in series through incandescent bulbs. Have not tried this yet. Is there any other way. I will also use GFCI's. Thank you.:

I use a stepdown transformer from 120VAC to 12VAC with a lightbulb in series with the output. I found 12V Edison based bulbs.

I have students wire up switch-lamp combinations (S1, S3, S4) and test these using the above power supply. The series bulb is so if they have a short, it just lights the series bulb.

This is not applicable to the GFCI project of course.

Is that what you are looking for?

Going from 120V to 90V has no real effect on the hazard.

When I was in trade school I introduced to the instructor the idea of putting an Edison fuse socket and a 120V light bulb in series with the control power for the motor controls. It saved contacts on switches, buttons and control relays when the student wired in a short.

 

[kwired]

It's 110vac thanks . And what's with the negative comments from the others.
I'm trying to keep contact voltage down when testing there projects . Try thinking from A to Z.
I thought this site had class. Those of you that are bothered by question don't reply.
I ask for help , guess not everyone knows everything you gentleman know. So one more time. Students , voltage , safely.

Your question was pretty vague, for all we know you wanted 90 volts at workstations in a computer lab, the equipment is probably not going to like that voltage.

90 volts is still too high, and putting a resistor in series still leaves you with 110 open circuit voltage, you will need a load and current flow before there is any voltage drop.

Suggest doing these projects with class 2 power supplies if you want things to be relatively safe to touch, you can still receive a fair shock though even from a class 2 supply, if conditions are right, most of the time it is hard to make happen though. I saw someone get a good one from a 16 volt doorbell circuit once, it was live pushbutton leads and they were washing brick with muriatic acid (which is common) which increased conductivity of things that normally wouldn't let much of 16 volts through.

 

[GoldDigger]

You are bringing me back to my college electronics lab days of benches with high current DC and ~400V current limited adjustable DC supplies.
Got quite a few DC buzzes, but we did not use any AC that I can remember (except from signal generators.)

Sent from my XT1080 using Tapatalk

 

[iceworm]

... And what's with the negative comments from the others. ...I thought this site had class. ..

Arrogant demeaning sorts. And then a group that appear to be wantabees that enjoy a rat pack. Useless - annoyingly useless.

It's 110vac thanks . ...

What exactly do you expect the students to do wirh this circuit?
Is there a lab book, a list of experiments?
How are the cubicles set up? Insulated benchtops?

I'd really recommend you answer in more than single short sentences. There is still not enough information to give you any help.

... I'm trying to keep contact voltage down when testing there projects . ...

I can't see that a series light bulb does that. If the leads are open-circuit, the voltage is still 120V.

The required available power (volts, amps) is dependent on what is required for the projects. Have you looked at the lab book to see what is required?

If you don't have one, maybe you should look for one. I would not recommend you set up the experiments unless you have a whole bunch of expertise in teaching the subject

So one more time. Students , voltage , safely .

Without more information - that is pretty useless. It's on you to tell us what you have in mind.

With no more than you have given us, I'd have to say, "Use batteries - nothing bigger than a few D cells or a 6V - 12V lantern battery

ice

 

[Ohms law]

It's 110vac thanks . And what's with the negative comments from the others.
I'm trying to keep contact voltage down when testing there projects . Try thinking from A to Z.
I thought this site had class. Those of you that are bothered by question don't reply.
I ask for help , guess not everyone knows everything you gentleman know. So one more time. Students , voltage , safely.

I did not mean any disrespect. I can't speak for everyone but I'm sure most would agree that we need all the information in detail on what you are trying to accomplish so we can give you an answer.

The part that I underlined is an example on being detailed.

 

[Ohms law]

With no more than you have given us, I'd have to say, "Use batteries - nothing bigger than a few D cells or a 6V - 12V lantern battery


ice[/QUOTE]

This sounds like the best and cheapest idea. I agree.