Re: International standards (2023 Update)

current

for a

time).

o.k. guys, thanks for the response.

Gain is gm * RL and from the graph we see that gm is about 3, so 3RL, so for an 8R speaker we get Av=24. For a 64R speaker, about 200.

l.b.

Hello, The ripple control Protocol Decabit is a very old (40 years)and simple one protocol developped by Zellweger Switzerland : (today Enermet OY). This protocol concist of 2 main parameters : the 1st one is the carrier frequency which is usually use from 125 Hz to 3000 Hz depending of the utilitie choice. The 2nd one is a suite of 11 bits impulses of each 600 ms. The 1st one is the start bit to warm up the receiver. After that the "telegram" is a combinaison of 5 bits "on" and 5 bits "off" which make of course 10 bits. If the telegram has not 5 bits "on" or 5 bits "off" its automatically ignored (fail in transmission). The combination of "on" and "off" give 126 different possibilties. The actions defined by those combination are defined by utility. Usually the code is written on the receiver and you can find the corresponding telegram on the following site :

Regards, melody

I am after a PWM circuit that can be used to help me build a two wheeled carry cart. I will want to be able to control the the speed of two motors so I can intiate turns. Skid steer is the term I think. Forward and reverse also required. Control of cart will be done from a handheld unit connected by umbilical. Unsure as to put circuits with the switches in the handheld or in the cart with the batteries and motors. Any advice or help would be useful. Please don't suggest looking for help in the library or search engines as their seem to be so many variations of the PWM circuits and I have no idea which would suit my task.

Many Thank

Gadget

Too bad thr spec doesn't list hfe :-0

--
Best Regards,
Mike

--
"Cord aneurism"?^)

I'm looking for information on how to build a high temperature sensor for the HAI Omni Pro II home automation controler.

Here's what I know:

1) The HAI produced temperature sensors send frequency to the board and the board converts the frequency to temperature 2) The formula for the conversion the board uses is T = F * 15 / 2 for conversion 3) the omni board does not handle temperatures over 120F, or 16 Hz

What I would like to do is design a sensor which will monitor temperatures higher than 120F (low pressure boiler water). Since the board can't handle temperatures over 120F, I see two ways to accomplish this:

1) send a Celsius temperature to the Omni instead of Fahrenheit. This would give me a high temperature of 120C or about 250F

2) send an offset Fahrenheit temperature, for example (T = T - 100). This would basically drop the first digit which is quite acceptable in this situation especially since I use F everywhere else.

Not knowing much about electronics, I'm not sure how to design this thing. I know I can us a LM34 to get the temperature but that outputs voltage (I only know that from google searches about temperature sensors for the SECU16). I don't know how to convert the voltage to frequency which matches the above formula. I also know the Omni sensors use thermistors based on 10k resistance and then calculate and convert the resistance to the appropriate frequency but that's no help to me since I don't know how that's done either. I know there are voltage to frequency converters but I have no idea how to hook one up to the LM34 to get the appropriate response.

Any help or pointers on how to proceed?

Thanks, Ray Manning

HI guys,

I'm looking for a bit of newbie advice re. switching circuits.

Basically I'm trying to create a book which can tell which page it is open on. One of the ways I'm trying is by using conductive paper for the pages - using each page as a simple switch so when two pages aren't touching the page knows its open. Crude I know...but it should be enough for what I need. The problems is that without using black carbon paper I've only managed to source anti-static paper with a very high resistance.

My question is, is there a way I can still use this low level of conductivity to form a simple switch?

Any comments would be gratefully appreciated as I am a little out of my depth!

Thanks in advance,

Hal Leemux

Paper:

@ 50% RH is 5x106 @ 20% RH is 6x109

I don't quite understand how to read an area resistance but I know that it doesn't even show on my multimeter! (I assume the above means at 50% humidity the resistance is 10 to the power 6 ohms??? so 10m??)

We have a remote outdoor sensor that is prone to failure (nearby lightning we suspect). It is only a couple transistors (2N3904, 2N3906), a couple

100V electrolytic and ceramic caps, a1N4148 and a few resistors. Unfortunately they are potted so I can't do a post-mortum. I can't use TVS or similar that shorts when failed because it will load the controller, which I can't modify.

Are there tougher transistors or other components that we can use?

Thanks John that makes a lot of sense now.. That is why you see area resistance written per square but with no value..... seems obvious once its explained!!

So from what you're saying I could rig up a simple Op-amp circuit that would allow me to switch with the paper? - that sounds great. I'll look at some circuits online and start playing around with it this evening.

Yes I have tried using conductive ink but its a bit of a messy solution. I am also trying to see if I could use some kind of conductive tape in the same way you suggest - possibly a transparent one with an indium tin oxide coating - but that is all if I can't get the paper to work really...

I've also got some alternative paper which says its resistance is 10/7 so I guess that must mean 100 milliohms which would probably be a bit better so I'll try that.

Thanks alot for your help,

Hal

out of his hat ?

having one large area ground plane on a pcb isnt always the optimum solution, if you have noisy part of the circuit close by, noisy ground currents can propgate noise voltage gradients through the ground plane (albeit rather small ). but this can cuase problems wich are hard to get rid of with any amnount of decoupling capacitors.

in order to get round this ive found it better to have an individual area of gnd plane for the smal siugnal stuff that conected to the rest at one point, of course it becomes important to select the right place to make the conection, but it stops the voltage gradient wich u can actualy see on a scope with a coax conected to a .1 "header" used as a probe.

Colin =^.^=

current

an

(even for a

time).

Vout = Vin/Rin*hfe*RL (asuming rin >>rb)

Colin =^.^=

I read in sci.electronics.design that Hal Leemux wrote (in ) about 'high resistance switch question', on Fri, 6 Aug 2004:

For a uniform sheet of conducting material, the resistance from one side to the other of a square of any dimensions is the same. For any rectangle, R = Sl/w, where S is the area resistivity, l is the length of the conducting path and w is the width of the path. If l = w, R = S, for all l or w.

You forgot the '5x', so it's 50 Mohms; 10 m is 10 milliohms. You can certainly detect 50 Mohms using a FET or a FET-input op-amp. You main problem will be keeping mains frequency and a lot of other stuff out of you circuit. A 100 nF capacitor directly across the input from your pages would be a good start.

6 Gohms at 20% RH is quite a bit more difficult; you probably can't use a printed board and surface leakage across components and wiring will be significant.

Have you thought of printing conducting strips on the page margins close to the spine? You can get much lower resistances, although the lower the resistance the more costly the ink is. But you would then be using ordinary paper.

--
Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Right- SURE YOU ARE!!!! It looks like you've been fantasizing about this fairy tale project for several years now........consider taking up tole painting or something.

The charger for my beard trimmer is a Whal wart. ...is it Friday yet?

--
  Keith

No, I can't tpye.

--
  Keith

current

for a

time).

Can we make this simplification with a current source load? i.e. treat Rc as infinity (theoretical R of current source) in parallel with R_L? Even with R2 going to Vcc?

[sotto voce] I guess.

And a ton of distortion. Don't fergitcher output cap :)

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Best Regards,
Mike

What is the sensor sensing? How long is the wire run from the sensor to the control? How is it actually run? What kind of wire is used?

John

Any of those circuits you found would most likely fit your task. It's really the circuit that is fed the PWM signal that is dependent on your application. Depending on the size of your motors, you'll need to amplify the power of the PWM signal to drive the motors, such as with an H-bridge.

However, another aspect of the overall controller to consider is complexity. You can make a PWM circuit using something as simple as some

555 timers, or as complicated as a microcontroller. Personally, I find the microcontroller route far simpler in the end, as it allows you to easily incorporate "intelligent" features into your design by simply reprogramming the controller. I prefer Atmel's AVR micros and the SP12 in-circuit programmer.

"Whal" -- From the same fine folks that gave you "Wein bridge"! :)