peter wrote: ↑19/07/2021, 19:55Geoff has wired all the leads and relabelled them .switched on and the signal lights came on then the loco started up moved a foot then stopped and nothing else happened.
Peter,
Did the red LED on the Over-current Protection Module Illuminate? If it did, then that implies that there is still some kind of a short on the network.
Penri,
Alternatively, it's possible that the slight volt-drop across the current shunt in the Over-current Protection Module has reduced the voltage to the train sufficiently to cause it to stop when the train reaches a place where there is more rolling resistance. Since the drop should be less than 100 mV I didn't think it would be a problem. If the problem still persists and the track voltage is around 8 to 10 V, then that is the likely cause. If so we will have to take the SD Card out and tweak the max_speed variable up a bit. I can do that in the car park if you can remove the card for me.
Today’s investigation:
Checked PSU voltages, all ok.
Plugged in 15V PSU, after a delay the underground train make its return journey twice before failing to make the third, the over current led indicator was on.
Powered down, did some checks but could see nothing untoward.
Powered up again, noted that red signals did not come on (at either end), but after a delay the train made several journeys before again tripping out the over current circuit.
It always fails in its start position on the left hand side.
I think we’re going to have to measure the dynamic current draw from the supply to see it there’s a transient there.
If there is a transient then we can adjust the trip point, as you know, simply by adjusting the pot. However, if it's a real spike, then maybe we can somehow suppress it rather than putting the system at risk by increasing the current limit to a uncomfortably high value.
The current setting is approximately 1.5 A and I understood from earlier posts that the normal current draw was less than 1 A.
Back on the 5th July Geoff wrote that the motor on the underground train had been changed, I didn’t read too much into it at the time but now thinking about transients / start up and what to do about them I’m beginning at ask myself what sort of motor are we dealing with and is it a different type from the previous one?
Going back to this morning, when the train ran, which is did on several occasions, there was never on issue during the first run after a power cycle of the Pi, the over current trip occurred after 2, 3, 4 or more journeys and the train was always stopped at the left hand end of the track, why there?
Don’t expect definitive answers just trying to stimulate thought!
Back on the 5th July Geoff wrote that the motor on the underground train had been changed, I didn’t read too much into it at the time but now thinking about transients / start up and what to do about them I’m beginning at ask myself what sort of motor are we dealing with and is it a different type from the previous one?
Going back to this morning, when the train ran, which is did on several occasions, there was never on issue during the first run after a power cycle of the Pi, the over current trip occurred after 2, 3, 4 or more journeys and the train was always stopped at the left hand end of the track, why there?
Don’t expect definitive answers just trying to stimulate thought!
I think your perception is right one day working fine switched off then switched on next day then the problems began . I have passed these comments on to Geoff and if he still cant log in then hopefully he will pass comment to me and I will forward them to the site
This morning I hung (not soldered in just relying on gravity) a 100nF capacitor between the base of the FET and ground (with the aim of slugging any fast moving spike transients from triggering the flip flop) and as a result the underground train did it's automatic cycles faultlessly and then I got around 7 manually triggered runs. I was feeling fairly please and was in the process of asking Peter to keep an eye on it when the over current trip went as the train was on the last part of it's return journey and is now stuck in the tunnel.
Peter and the guys were preparing the layout for the day ahead so I decided to call a day on the experiment and come back to it when I could have just the underground working.
I'm not sure if the capacitor actually made any difference or I was just lucky.
I'm now away for a few days so will return to the issue mid next week.