| Electronics > Projects, Designs, and Technical Stuff |
| Slip Ring |
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| m3vuv:
why not use slip rigs and brush block from a scrap car alernator?,cheap ready made solution. |
| CatalinaWOW:
Slip rings can carry high bandwidth and low amplitude signals. If you put enough time, money and energy into it. Other than the ones used for telephone line cords I have no experience with low cost rings. Most of the companies i worked with only provided custom assemblies so the costs are stunning. All of the good slip ring assemblies I am aware of use multiple brushes on each ring to reduce the impact of contact bounce, and even just resistance variations across the contact. Some have as many as eight brushes. To the extent that you can making the impedance of the driven circuit as high as possible consistent with bandwidth helps reduce that contact resistance impact. It isn't terribly difficult to make your own slip rings for low speed applications like this. Lay out a PWB with one or more circular rings. You can go double sided though single side works too. Stack these disks on a shaft with a non-conductive spacer. This will be the rotating side. You have to run wiring from the rings along the axle to your destination. The "brushes" can be salvaged from a number of sources, including defunct DVM (from the selector switch), fuel gauges, or the emi shields from cabinets. Remember to use more than one per signal with all brushes on a signal paralleled. If you have access to a lathe for machining a fascinating variant is to copy the power rings on the ISS that connect the rotating solar panels to the non rotating station. Rather than a brush the rotating and stationary part are connected by a hoop of conducting material that is slightly compressed in a track somewhat like the races on a bearing. They use three of these hoops spaced 120 apart, and obviously have some mechanism to keep them at the 120 degree spots. Minor variations in hoop diameter would have them running into each other otherwise. |
| luiHS:
I also thought about making my own rings with PCB board and brushes. The PCB has no problem, I design it and the Chinese make it for me, but the brush system is more complex. It is not about manufacturing a unit using some components taken from scrapping parts, because once I have designed this product I will have to manufacture it in a certain quantity, therefore I cannot depend on scrapping parts. I suppose that the brushes with their spring and their charcoals can be bought from the Chinese, the case is if it is worth designing and assembling my own slip ring, instead of using a commercial one. Slip rings in the Chinese cost between USD 5 and 16 per unit, and are ready to use. In the attached image, someone already did something similar to what I need, his ferris wheel is for a model of trains, mine is not for that application, but it is similar. Theirs is simpler because it only transfers power for simple LEDs, in my case they are APA102 digital LEDs and I also need data and clock signals, in total 4 signals, but if I duplicate data and clock to avoid problems due to bad contacts in the brushes, I already need a minimum of 6 contacts. The use of the system to couple two annular coils inductively also complicates the design to do so with some frequency. Unless these annular coils I can also do them with PCBs, in that case the solution would be quite good, because in a single PCB I could put three annular coils that would fit with the other three annular coils on the ferris wheel PCB. Maybe try it. |
| luiHS:
Looking for information, what I found interesting for the motor to use with the ferris wheel, are these PCB stepper motor. I do not know if there is something commercial, but the design does not seem complicated, I understand that there are two round PCBs, one with the printed coils and the other with permanent magnets, it does not seem very complicated to do, although if there are already facts, much better. Another thing is the power they may have, if it will be enough to move my ferris wheel. Anyone have experience with this kind of stepper motors, is it a commercial product that can be bought? https://hackaday.com/2018/03/28/a-brushless-motor-on-a-pcb-made-from-pcb/ |
| beanflying:
Given the rotational speed you will likely want KISS and use a DC brushed motor for maximum torque at slow speed anything from a simple relay to a FET/PWM from a micro will do you. Either that or you will need at least a double reduction and more control gear if you go brushless as their torque on startup is not as good. If you strip a CD drive some of those will have a PCB type brushless and some gears but I wouldn't go down that path because of the control complexity. |
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