Advice please from those who understand electronics

[chris m01]

I use the old Aristo train engineer for track power and a Deltang tx22 with Rx65 receivers for my battery fleet. This is all fine and I am very happy with it.
I am aware that one day the train engineer will give up on me and I like the knob control on the Deltang (or RC Trains) transmitter. So, based on comments in previous threads I bought myself an Mtroniks 24volt Viper HV ESC which I plan to use to provide power to the track. I have a couple of technical questions.

1. So far I have tried it with a DSSS standard radio control TX and RX to control track power and it worked exactly as expected. I then connected an RX65 receiver in place of the standard radio control receiver using P8 as the trigger for the ESC and using the power from the ESU to power the RX65. The RX65 is bound to a TX22. This works but sometimes there is a delay in power being applied when the knob is first turned. Once the power comes on stream control is perfect. I'm not sure whether there is something built into the servo output on the RX65 to prevent switching too quickly. This delay does not occur when using the DSSS TX and RX. This isn't really a problem as all I have to do is apply wait about five seconds from stopping before starting again but I wonder if this indicates some sort of technical issue which could be a problem later.

I'll post the second question in minute

 

[chris m01]

Question 2.
Crest used to sell a nice little PWM to linear converter. Looking at photos on the web the circuit diagram is something like the one shown below. Please forgive my poor circuit drawing. The use of back to back electrolytic capacitors means that it can cope with current in either direction. Just wondering if anyone knows where to get a toroidal choke and what the other capacitor is as this circuit looks pretty simple. Or has anyone got any better circuit ideas. There are many simple ones on the web but they seem to only be able to cope with current in one direction and its hard to know what values the components need to be for 24 volt up to 10 amps.

 

[chris m01]

Question 2a
I have an old TE receiver which of course has a PWM to linear converter on board. I reckon the components for this are shown on the photo below. The switch at the bottom of the photo is the PWM to Linear on off switch. There appears to be back to back capacitors connected to this switch and something between the capacitors and the relays that may or may not be a toroidal choke next to them. It could of course just be a nice big resistor but I think it is probably a choke of some kind which would probably be the right size for the job. I wonder if I could build the required circuit by re-using the components from this board and make a circuit like the one shown above? Any advice from those who understand electronics would be much appreciated.

 

[PhilP]

Hi Chris,
1. Could you provide a diagram of how the bits are connected?
It could either be 'inertia' on the servo output, or not waiting for Tx and Rx to sort themselves out?? - The Rx65 needs voltage, and to be 'on' before it can do things.. Your description hints the power might be after the ESC??

2. Really need the PWM frequency to be able to sort out values for you..

2a. Yes, they are the components of the TE filter.

NOTE:
I think you will find the filter is supposed to be limited to 5 Amps?

 

[chris m01]

Thanks Phil
The frequency is 3k.
I think the TE instructions say it can take 10 amps with a fan attached. I tend to use mostly one and sometimes two USAT locos together. They tend to use less than 2.5 amps each even with the smoke switched on.

 

[Greg Elmassian]

No one in the UK carries the PWM filters?

If you get stuck, I can measure mine...

Greg

 

[Neil Robinson]

Chris, according to George Schreyer's site the linear/pulse change uses a single polarised 2000 micro Farad capacitor.
For PWM it is switched in across the incoming supply proving additional input smoothing. For Linear it is across the output just prior to the output polarity changeover relays.
Greg, is that the 0.5A unit? Do you have a circuit that could provide a linear output from a typical electronic speed control rated between, say, 5 to 10 A?

 

[Deleted member 4232]

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