Improving Align/Central_machinery power feed velocity control

why don't you look on ebay for a Minarik DC controller - I used to have a lot of them but they are all gone - I've had good luck with Minarik - you can look at specs on their web site - should be able to get one for $25 to $35

Feed drive units have been discussed here in RCM before, and IIRC, someone modified the original circuit for a lower speed setting, but I don't recall any other changes.

Probably the simplest electronic variable speed control for a universal motor is the triac and diac ciruit. While this circuit provides varaible speed, it doesn't regulate the speed. The HF router speed control is a triac/diac circuit.

Next might be a simple SCR and PWM pulse width modulation IC, but again, no precise regulation of speed. Similar to a variable speed drill circuit in a quality drill.

As circuit complexity increases, more parameters come into play (work), and very good speed regulation becomes realized.

You should try to determine the motor's full voltage, and then the amp and/or watt load that the motor produces, to decide which circuit would be best suitable for the feed motor. Since the original controller is a SCR circuit, the motor brushes are possibly for DC (no way to assume, since it probably came from China).

Bill's suggestion of a Minarik controller is good advice since they are reliable and fairly inexpensive. One thing you can probably be sure of is that a better control circuit is going to need to be connected externally, so you'd be wise to locate a sturdy metal enclosure to protect the speed control and yourself.

There are various eBay sellers that sell small, inexpensive regulator modules, but I haven't used any of them, so I can't make a recommendation.

A couple of safety devices should be considered, in case they're not inluded with a control that you might find; a fuse to protect the circuit, and a fuse (at least) or other device to protect the drive motor. A thermal protector for the motor would provide an extra level of protection/insurance, that usually isn't provided in many motor driven devices.

I searched and could not find anything on power feeds except installation questions. One complaint I do have is the very small usable range of the speed pot. I do see that the 150 inch pound schematic shows a dual SCR for full wave operation. I'll try Bill Noble idea of a controller off ebay. What I really would like would be a controller that has a shaft encoder input, but gosh that turns a half day task into weeks to get it right. There's quite a bit a gear reduction from the motor to the shaft drive, I guess if all else fails I'll design my own, but that turns into more effort then I want. ignator

Thanks for the replies.

The limited speed range sounds like what the old post/discussion was about, now that you mentioned it.

It's been a while since I looked at the diagrams of the internal parts of the feed drives, so I don't remember where the circuit board is located, but modifying or upgrading the existing circuit board might be an option if there is enough space, and if you can identify and locate some suitable components.

The DC motor drive controllers such as the Minariks and several others, may have several settings on their circuit boards. This generally allows them to be used in more types of applications. Getting the manufacturers' setup instructions and specifications (can often be found online as a PDF file) should be helpful for setting the adjustments such as current limit, min/max speed, etc.

BTW, there are two common DC motor drive output voltages.. 0-90VDC and

0-130VDC. Generally, the 90V output is a 120VAC input drive, and the 130V drive often requires 240VAC input.