[astro]

I know a fair amount about digital in general, but not the specific implimentation with slot digital.

But I understand scalextric uses PCM - pulse code modulation. (there are a few methods of encoding digital signals) Usually, this method involves turning the current on and off, not reversing it, ie switching between (say) +12V and 0 V, or it could be implimented to switch between +12V and +10 volts. Most of the digital signals I have come across operate in the region of 48KHz or more, 48000 on and offs per second instead of 50 on AC. rates can go up to megaHz though, and each hi voltage represents a binary 1 and each low voltage represents a zero. each 'package' or set of numbers will probably include an address or car number, so the car the rest of the instructions belong to will know to pay attention to the rest of the contents.

Since a scalextric rail with lots of joints isnt the ideal conductor for high frequency square waves, the frequency might be a lot lower, dont know. But the higher the frequency, the easier it should be to filter out for the motor.

Hope this is clear, and not further obfusciating the issue

 

[astro]

chopped is slang, the term is 'pulse code modulated'. Modulation is usually the adding of one signal to another, and what is added to the dc is 'pulses'. In theory, the digital modulated signal will be a square wave with distinct changes of state from hi to low voltage, at irregular coded times.

What is usually ment by ac is a continuous regular sign wave, or oscillation, always changing voltage between +12V and -12V (for example). Main reason we have AC mains is that for technical reasons, less electricity is lost down the extremely long distances between power stations and ppls houses.

 

[astro]

thanks fergy, thats clearer

 

[astro]

sorry for saying it wasn't AC, tropi, looks like i was essentially wrong!

 

[astro]

digital signals can be modulated onto ac, prob not as DCC or PCM (there r a lot of modulation schema), and i believe on the mains systems they use very high frequencies approaching RF. For this to be legal, u have to filter ur mains very thoroughly, cos its illegal tho very easy to contaminate the grid with ur modulated signals. My understanding is that the modulated frequency has to be a good order of magnitude greater than the carrier frequency (50hz in the case of mains), and my suspicion is that due to scaly rails, joints and braid contact, the frequency for this must be relatively low