Descargar Solucionario Boylestad 10 Edicion Pdf

#Descargar Solucionario Boylestad 10 Edicion Pdf series

The problem was already described on this forum, and in some other national forums. The cutoff micro switches seemed to be responsible for that, as they have to switch up to 1A rms from an inductive load (if the motor is fed with 16V AC), which is beyond their specifications. In order to validate that hypothesis, I opened a microswitch (cutting the top with a cutter) and energized the motor. The pic below shows a spark between the 2 contacts of the switch. The question is: why some users have no problems, even after many years? (Note: As the switch time can be as low as 10ms, reducing the feeding pulse duration to 100ms or so is useless in this case) Sooner or later, that sparks will lead to a failure. I read somewhere that the problem occurs only with old Marklin motors. connect a capacitor in parallel with each switch (but there is still a small spark, even with 500nF) May be the quality of the Cherry microswitches ?Īnyway, if we don't want to take the risk to get a failure on a permanent layout, I see 4 solutions Mine were built in 19, then not that old.

#Descargar Solucionario Boylestad 10 Edicion Pdf series

short the switches and use only current pulse for driving the motor.Ĭonnect a back-emf diode (or 2 x 30V zeners in series if the motor is used in AC, or a 30V transil,) in parallel with each switch. In the last 3 cases, it's necessary to open the motor. The problem with the 74490's is a bit (or a lot) more complex then meets the eye. When your turn-outs don't switch over there can be a number of causes. The first and most common one is just lack of electrical power as is often mentioned also by Märklin themselves. More often then not aggravated by a sticking or dirty turn-out mechanism. The second cause certainly with the older 74490's having a single double-action microswitch, is. It causes the solenoid plunger to bounce back at the end of its travel. An additional cause can be the microswitch itself. Either it switches off too early or not soon enough in both cases leaving the turn-out at a half-way position. In reality there is a delicate balance between the speed of the moving plunger and the moment the solenoid is interrupted by the microswitch and we find ourselves again confronted with root causes 1 or 2. Meanwhile, most märklinists know by now that shorting out or removing the microswitch solve all these problems so we automatically assume that the microswitch is the culprit. It isn't but taking it out makes the switching action far more tolerant for both root causes numbers 1 and 2 and far less tolerant for analog switching.Īs for contact arcing as described by Fred and many others in various places, indeed that causes contact wear and thus a reduced life span. However, this type of switches normally have a lifespan of 100000 duty cycles, at rated load, even the el-cheapo ones.

So if that arcing cuts that life span in half, you're never going to use it up anyway. okay yes, YOU are the exception :-)īut hold on, there is yet another phenomena. And it is back to root cause number 1: not enough power and infrequent switching. That results in a build-up of dust, dirt on the contact surfaces which is not burnt away by the switching action and, indeed, by arcing across the contacts. For more interesting literature on this subject see:Įdited by user 10 February 2011 23:19:50(UTC) So, a bit of arcing is indeed beneficial for reliable switching action and that arcing only occurs when sufficient power is applied at. Märklin has been working on these motors and modifying them ever since they were brought out. The new version 74491 according to Märklin has a new type of switch in them. What I tried to point out in my previous post were the causes of these problems. Once you have these motors built in you don´t want them to fail after only a short period of time. To prevent that, there are a number of things you can do:ġ- Take out or short out the microswitches but only if you switch your turn outs digitally with controlled/limited max. (not possible with the old keyboard and 6021 or Intellibox 1).Ģ- Use the Viessmann 5211 decoder with their DC power module (5215) to power the motors. Or use any decoder, including good old K83 and feed the motors separately with 18-22 Volts DC similar to the Viessmann setup*ģ- If you use analog switching use a separate 16V transformer dedicated to switching your turn outs only and use original purpose built pushbutton switches, Märklin or another good quality brand. Don´t put your elbow on them.Ĥ- Always make sure that the mechanisms are clean and free. Collected dust combined with sticky oil dripping off your loco´s or coaches can be detrimental.