lowering voltage

[tdub]

I hope that this isn't too much of an obvious question, I have a 120v strobe light that puts out 350 v dc to the lamp. It also has around 150v dc between one of the lamp leads and the lead that does the grounding for the strobe effect. What i am trying to do is get the lamp voltage to 9v dc. I'm pretty sure that I need to use a resistor to do this but not quite sure how big of one and any help in trying to figure this out will be greatly appreciated. I apologize again for the obviousness of my question. (obviously is not obvious to me )

Tim

 

[Resqueline]

You mean you want the trigger lead to have only 9V? A resistor can't do that. What are you intending to trigger it from?

 

[tdub]

Thanks for your quick response. I'm not sure what you mean by "What are you intending to trigger it from" I want to use it as it is but not run a lamp with it. I want to put it into a circuit that is running at 9v. I hope this is enough info for you. Thanks again Tim

 

[TBennettcc]

...so you want to remove the lamp from the strobe light housing, stick two wires into the housing, and have the strobe light trigger some external circuit at 9V?

...why not just use a 555 timer in astable mode?

http://www.kpsec.freeuk.com/555timer.htm#astable

...or are you saying you want to run the strobe light enclosure from 9VDC, instead of 120VAC?

 

[tdub]

thanks, that looks like that will work. One last question though. I want to put a pot in it so I can adjust how fast or slow it triggers. So would that work being that I would only be replacing 1 of the resistors? And which on would be better to replace?

Thanks again

Tim

 

[TBennettcc]

I still have no idea what you are trying to do...

Are you saying the 555 timer will work? Or are you still messing around with the strobe light enclosure?

Replacing one of the resistors? Huh? Where?

If you're going to use the 555 timer, you need to figure out the lowest and highest frequencies you need for the triggering, then put those into the formulas and calculate the necessary resistances for a potentiometer.

Why don't you post the full details of what you are trying to do, instead of posting vague segments? Then we might be able to get a better idea of what you're trying to do, and possibly suggest a (better) solution?

 

[tdub]

ok, I am trying to build a circuit that will operate at 9v. I want this circuit to act as a switch to interrupt an audio signal. I tried using the strobe to do this but there was too much voltage and all i got was pop pop pop for the audio. So, I put a toggle switch in the audio circuit and manually turned it off and on and it worked perfect with no noise. So I am hoping that this timer might be what I was looking for. I also want to be able to adjustable the speed in which it interrupts, that is the reason for replacing one of the resistors with a pot. I hope this clears things up and again thanks for your help, Tim

 

[TBennettcc]

So do you want a circuit that is constantly switching on and off, or are you looking for a switch that just turns it on and off every once in a while?

If you're looking for constantly on and off, I think the 555 astable should be able to do what you want. If you're looking for just once in a while, take a look at the other 555 timer circuit on that page, specifically the 555 monostable.

Like I said before, you should be able to plug in the frequencies you're looking for into those formulas, and get the values of a pot that will do what you want.

 

[tdub]

ok thanks and ya i'm looking for it to be constantly going on and off, so i guess i have to figure out my time values and go from there. I am still a little confused about where to place the pot, if it should replace r1 or r2 in the schematic for the 555astable. thanks again

Tim

 

[tdub]

ok i ordered this timer, will the leads on it be identified as 1, 2,3... and so on? If no, how do I identify them?

Thanks again

Tim

 

[TBennettcc]

If you're talking about the 555 timer integrated circuit (IC), all ICs have either a half-moon shape, or a dot. These shapes indicate pin #1. After you know where pin #1 is, the next pin counter-clockwise is pin #2, etc., all the way around the chip.

This link has a good picture (even though the IC in the picture has 16 pins, and yours will only have 8...)

https://wiki.ittc.ku.edu/ittc/Image:EECS140_Lab1_IC_Orientation.gif

 

[tdub]

thanks for the infor and you quick reply

Tim

 

[tdub]

ok I received my parts for this project and put it together today, but it didn't work and I am stumped as to why. What I am doing is trying to use this time to interrupt an audio signal. I am using a 200k pot for r2 and a 10k resistor for r1. I also picked up all of the caps that the print shows to use because I wasn't sure which one I needed so I jumpered them into the circuit one at a time. the caps are a .001uf, .01uf, .1uf, 1uf, and 10uf. I hooked it up exactly as it shows here

http://www.kpsec.freeuk.com/555timer.htm#astable

I think that the 0 voltage is negative, someone correct me if I am wrong.

Pin 5 i took right to negative with no cap.

If I new how to draw a schematic or layout on here I would do that but I don't know how to. Everything else in the link I hooked up just like it shows and when I turn it on all it does is makes a constant noise (almost like a short sound) that totally drowns out the audio signal. I hope that I have given enough info, if not let me know.

Thanks for any help

Tim

 

[(*steve*)]

Perhaps you should tell us what you're trying to do. It sounds like the circuit is doing pretty much exactly what I might consider it would.

 

[MagicMatt]

This thread actually scares me. You took a strobe light and linked it up to an audio signal and it didn't blow something up? Do you have hair like Einstein by any chance?!?

It sounds like you're trying to basically make an audio signal chop on and off, as if you were disconnecting the audio signal repeatedly then reconnecting it, or turning the volume up and down on your amp quickly.

The simplest solution I can think of is using the 555 to control the gain of an audio quality Op-Amp. The 555 provides the gain control, and effectively turns the volume up and down.

Please don't wire up and more high voltage devices up to your audio equipment, or you'll be in line for a Darwin Award.

 

[tdub]

not sure what a Darwin award is but thanks. I am an electrician so I understand high voltage and how to work with it. With that said, yes that is exactly what I am trying to do is turn on and off an audio signal. My latest try was today and I used a 555 timer to control a mosfet 510 and I did get some audio through at slow speeds, but there was more noise than audio. When I turned it up to higher speeds the audio signal was completely drowned out. I am learning as I go and throwing parts at this to get it to work, and I am getting closer but I am still a newb at electronics so I am not really sure what an audio quality op amp is. If this is what I need instead of the transistor I am all ears. Thanks for your help and I look forward to some more info.

Tim

 

[MagicMatt]

Ok, genuine question, please don't take this the wrong way, but... how can you be an electrician and not know about things like Op-Amps and 555 timers? I don't mean that to be rude, I genuinely want to know. I am considering re-training myself as an electrician (I am bored with web design and IT, been doing it since age 5), and I thought knowing the electronic circuit design would be helpful... am I heading in the wrong direction?

The audio OpAmp is just a term used to describe OpAmps that have low noise and can handle audio frequencies nicely. That typically translates to a high slew rate (to avoid distortion), flat response over 20Hz-20kHz (or flat-ish), and fairly decent output current. It's surprising how many OpAmps that actually rules out... of course it also depends how fussy you are.

I have very little knowledge of the electronics as I'm a beginner myself. Personally I like the LM386 simply because it's the first one I ever managed to get working, and since then I've always found it to be a great performer for very little money.
http://web.mit.edu/6.s28/www/schematics/lm386.htm

I don't understand it enough to give you a circuit, but Pin7 of the LM386 can be used to provide a mute if it's connected to Vcc or GND, so I'd imagine something could be done with the output of a 555 on that pin to provide you with the chopping you're after.

The effect you're creating is typically achieved in a studio using a "Noise gate with sidechain" ... I have one for my guitar, but it's all surface mount and beyond my expertise to decode the circuit.

 

[tdub]

Matt, knowing dc circuits is something that we looked at in trade school and also in the apprenticeship, but it was more of a stepping stone towards ac circuits. With that said, most of the work that electricians work on is lighting and power with some distribution. Some specialize in control wiring, but unless you live and/or work in an area that has a lot of factories that have control in them, an electrician rarely ever sees this sort of thing. I live in the twin cites area of MN and we are mostly residential and light commercial area. So if you are lucky enough to land a gig where you get to work with control, and even if you do, you will still just follow a print that an engineer has put together, you will rarely get to work on circuits like that. Check into it where you live and find out what kind of work is out there.

Now with all of that said, I do understand dc, for the most part. But there is soo much different little do dads out there, that I just don't know what to pick from or what is available to me. How does a person find out this sort of thing, other than just getting your hands dirty and trying it out and luckily it will work and if it doesn't then your on to the next try.

The strobe was a step in the right direction, then the 555 was suggested to me and once i put in the transistor it all came together, and it worked electronically the way I wanted it too, but it had too much noise, now my next step is to research these audio quality op amps or maybe try putting some kind of noise gate into the circuit. Not sure which way will be best. If anyone has any suggestions, they are much appreciated, and I will keep posted my results.

Thanks

Tim

 

[(*steve*)]

If you;re trying to turn an audio signal on and off then you need something that will switch to a high or low impedance between its terminals on receipt of the signal from the 555 (which is fine for this).

There is a device that is made to do this. It is a 4066. This CMOS IC contains 4 analog switches that turn on and off in response to a digital input. You need only 1 of the 4, but the chip is very inexpensive. Look here.

edit: MagicMatt - An electrician is not an electronics technician. There is no particular reason why he should know more about a 555 than anyone else outside the electronics industry.

 

[TBennettcc]

If you actually want to learn theory, etc., a good starting point is "The Art of Electronics" by Paul Horowitz and Winfield Hill. Considered by many to be the "bible" of the electronics world, even though the book is a tad dated, most of the material in it is still very much relevant (how much do the properties of electrons change over time?)

Another good website that I've found useful is: http://www.opamp-electronics.com/tutorials/dc_theory.htm

Good luck.