• Scam Alert. Members are reminded to NOT send money to buy anything. Don't buy things remote and have it shipped - go get it yourself, pay in person, and take your equipment with you. Scammers have burned people on this forum. Urgency, secrecy, excuses, selling for friend, newish members, FUD, are RED FLAGS. A video conference call is not adequate assurance. Face to face interactions are required. Please report suspicions to the forum admins. Stay Safe - anyone can get scammed.
  • Several Regions have held meetups already, but others are being planned or are evaluating the interest. The Ontario GTA West area meetup is planned for Saturday April 26th at Greasemonkeys shop in Aylmer Ontario. If you are interested and haven’t signed up yet, click here! Arbutus has also explored interest in a Fraser Valley meetup but it seems members either missed his thread or had other plans. Let him know if you are interested in a meetup later in the year by posting here! Slowpoke is trying to pull together an Ottawa area meetup later this summer. No date has been selected yet, so let him know if you are interested here! We are not aware of any other meetups being planned this year. If you are interested in doing something in your area, let everyone know and make it happen! Meetups are a great way to make new machining friends and get hands on help in your area. Don’t be shy, sign up and come, or plan your own meetup!

Search results

  1. JohnW

    Bridgeport Mill Tachometer

    I haven' been around this forum for a while (not for any good reason), but as it turns out Brent H was over at my place picking up various Opel parts for his new project (I am involved with Opels as well) on the Monday after he picked up his new project and had the meetup. I was actually in...
  2. JohnW

    Single phase to 3 phase conversion on Modern GH1440W lathe

    I did almost exactly the same thing for my VFD'd motor. Great minds obviously think alike! My fan is a very powerful 24V unit (from an old IBM mainframe) powered by an old 20V laptop supply. It is powered by a small relay that is connected to one of the VFD outputs. I programmed the VFD to turn...
  3. JohnW

    Adding transformer to a 3ph rotary system

    It is possible to tap into the windings to reduce voltage. I've done that a couple of times with single phase transformers in the past to get a slightly lower secondary voltage. You only have access to the outermost winding though. Are the three phases wound consistently so you can modify each...
  4. JohnW

    Single phase to 3 phase conversion on Modern GH1440W lathe

    That is a cool feature that automatically lowers the PWM frequency as the heat goes up. It is unlikely that most hobby lathes would have overheating problems anyway, even at high frequencies. The current through the IGBT's (proportional to the heat) is also proportional to the amount of load...
  5. JohnW

    Electrical question

    The key is the concept of a "circuit". The power (conventional current) will go from the positive supply to ground (negative supply). The power is then "boosted" back up to the positive supply voltage by the supply (adding energy), and it goes around the circuit again. There needs to be a...
  6. JohnW

    Single phase to 3 phase conversion on Modern GH1440W lathe

    Switching circuits are usually more efficient at lower frequencies. The goal is usually to try to get above 20KHz since most noise generated by that is inaudible to humans. For old people the limit is close to 12KHz. A young'in may complain about the high-pitched squeal from the VFD / wiring /...
  7. JohnW

    Electrical question

    The lights would have a micro controller based controller in them. These days it is way cheaper to use tens of thousands of transistors running some software in a micro-controller to do a simple job, even though it seems like overkill. A small embedded processor and a transistor costs much less...
  8. JohnW

    Variable speed for angle grinder

    Regular dimmers are not designed to switch inductive loads. Significant voltage spikes can be generated when they switch the power on and off to an inductive load. That will work to some extent but usually not for their full rating. i.e. running a 1 or 2 amp motor on a 10A rated dimmer might be...
  9. JohnW

    power supply/controller for spindle motors

    There is really no difference between the 'external analog' and 'potentiometer' speed connections. The point is to provide a 0-10V signal to that input of the controller. It does not matter how that voltage is created. The 0-10V signal is a very low current signal. When using a pot, (the photos...
  10. JohnW

    power supply/controller for spindle motors

    The controller definitely requires DC input. The really big hint on that is the + and - marked on the power terminals! Feeding 120V AC in there will extremely quickly let out the magic smoke, and probably in a very impressive way. More specifically it requires somewhere between 24 and 50V DC on...
Back
Top