555 timer question

[spke1816]

I know the output of a 555 timer puts out a specific frequency. I'm not sure what that is currently, but I've found one website that said it was 36KHz, is it possible to build a circuit with two 555 timers to get a different frequency output?

I'm looking for a simple way to create two differnet fequencies to send through a transmitter and I know that using a 555 timer for one is a simple and efficient way to get that. If anyone has any insight that would be much appreciated. thanks in advance

I do have another thread trying to get information other aspects of the same projects here: https://www.electro-tech-online.com...cally-controlled-toy-train.119217/#post979971

 

[ericgibbs]

hi,
A 555 can be configured to produce a wide range of frequencies, by simply changing one or two component values.
Look at this link, if you download and install the calculator, you can easily work out the frequency/timing.
https://www.electro-tech-online.com/blogs/ericgibbs/125-simple-7555-cmos-timer-calculator-v1-2.html

 

[spke1816]

I Will down load as soon as possible. That appears to be exactly the thing I'm looking for. Thank you

 

[DerStrom8]

You could connect the 555 to a variable resistor between pin 7 and V+. By adjusting the pot, you will be able to change the frequency. That's probably the easiest way to go if you need an exact frequency.
Der Strom

 

[spke1816]

would using a crystal oscillator be more reliable as well as simple? I know most are two pins, is there a + and - lead? I haven't really used them with the exception of a couple projects that had them built in already

 

[ronv]

Unless you need the accuracy of the crystal the 555 will probably be more versatile. What frequency do you need? Tell us a little more about the project.

 

[carbonzit]

Theoretically you could use a crystal (I'm sure someone will correct me if I'm wrong here), but since they're only available for frequencies in the megahertz range, I doubt you could use one.

 

[spke1816]

As I've mentioned in my other thread I'm trying to build a transmitter that will send out only two frequencies. When the receiver gets frequency A the motor attached to a toy wooden train runs to move the train forward when frequency B is received the motor will switch polarities and run the train in reverse.

The receiver needs to be small enough to be attached to the train as well as the motor and any other necessary circuitry to run said motor

The reason I was thinking of the crystals are because they can guarantee a value and would take up less space in the circuit compared to using a 555 timer.

here is a battery question- if the transmitter runs off of a 9v batt and I placed a switch in series, when the switch is off my understanding is this would act like an open and the resistence would be infinite so there would be no current flow. Would this still cause a drain on the batt? And is my understanding on this correct?

 

[carbonzit]

The reason I was thinking of the crystals are because they can guarantee a value and would take up less space in the circuit compared to using a 555 timer.

A crystal by itself does nothing: it needs to be connected to an oscillator circuit of some kind to function, so actually a 555 might end up being smaller.

here is a battery question- if the transmitter runs off of a 9v batt and I placed a switch in series, when the switch is off my understanding is this would act like an open and the resistence would be infinite so there would be no current flow. Would this still cause a drain on the batt? And is my understanding on this correct?

Yes, an open switch is "infinite resistance", so no current will flow through it and the battery won't be drained.

 

[spke1816]

I Didn't know shoot the oscillator circuit for the crystals. Thanks.

 

[carbonzit]

This might be a little premature, and I apologize if it's over your head, but you might need to think through your scheme a little more thoroughly before starting this project.

This receiver, from Micrel, is probably fairly typical of the type of receiver you'll end up using (ASK/OOK). It's pretty much a "plug-and-play" device so far as receiving your signal on your train goes (they refer to them as "antenna in, data out" devices, meaning that all you need to do is hook up an antenna and a few other components and you can get data out of it).

Unfortunately, like much of life, it just ain't that simple. You can easily get data into our train: the problem is how to interpret it. You proposed using 2 separate tones. This could work, but you'll need a tone-decoder circuit to make this work. Another approach is to use another kind of datastream, like some kind of simple bit-encoded stream for your commands.

You also need to keep the limitations of the transmitter and receiver in mind. For example, the MICRF001 is only capable of decoding data up to 4.8kHz. Again, this doesn't apply to all available receivers, but it may be somewhat typical. You can shop around and see what you can find.

 

[Shyamal]

Very interesting thing 555 timer.

 

[carbonzit]

Actually, O.P. (original poster), if you look at page 8 of that datasheet they show you how to make a complete receiver & decoder with only 2 chips (the Micrel receiver plus a HT-12D decoder from Holtek). Very simple.

The transmitter would be equally simple. All you'd need to transmit your commands would be a couple of switches. On the train, you could just connect two of the decoded data outputs to your devices on the train, using optocouplers, transistors or relays. It would all be a lot simpler than generating tones and then decoding them.

The radio chips have multiple addresses, so you'd have to set the address on the transmitter and receiver to match. Very simple: if you're using a fixed address, just hard-wire the address lines to your address. If you have multiple things you'd like to control (like more than one train), then you can set the addresses with DIP switches.

I'd recommend this setup.

 

[spke1816]

in the next week or so I'm going to post the schematic we're working with as a basis as well as the changes we're making to it.

 

[Boncuk]

Hi,

if you have an AVR programmer you could create NE555 circuits using an ATTiny25.

The monostable version is retriggable.

Both versions IMono and IMulti can use an external crystal for optimum accuracy and frequency stability.

You might download the article + free software from https://www.elektor.com.

The title of the article is I555.

Boncuk

 

[spke1816]

I just wanted to say thank you to everyone for their suggestions, you've all given me alot of things to check into a think about. TO carbonzit, I took a look at page 8 of the manual you gave the link for and that looks very doable.

Another think I was thinking about would be using a microcontroller, but I am not very skilled in writing my own code. I passed the class on it, but still didn't quite understand what I was doing, same goes with c programming. connecting a microcontroller i had no problems with, it was just the coding itself.

The garage door styled circuit is what gave me the idea for sending only one frequency. the transmitter seems simple but i am having trouble finding even sample schematics on that to base my design off of one, same goes for a garage door reciever. With the garage door I realized that only one frequency was being sent out and depending on the state of the garage door it would stop moving, move forward or move in reverse, which is exactly what i'm looking for with the train