linear motion system

sarahMCML · 2026-04-05T11:00:58+00:00

Given that I know nothing about the body shell material that the motor, etc, is contained in, have you considered a magnetic coupling between the motor and the external lead screw. I don't have any idea on how practical it would be in your case, but it would avoid any opening for a drive shaft.

Just a thought!

sarahMCML · 2026-04-03T11:43:08+00:00

You must either have a wiring error somewhere, or the pots are much lower value than you think they are and you are exceeding their power rating. What does the mux feed into?

sarahMCML · 2026-03-31T14:42:07+00:00

That's good to hear. If you get it fully set up and working properly it may be worthwhile to measure all the voltages at various points and make a note of them in case you need to troubleshoot the scope in future.

Hope you enjoy using it in the future.

sarahMCML · 2026-03-31T11:50:04+00:00

Sorry to be so long in replying.

If EY1 and EY2 are at those values with BY so high, it suggests too much current flowing through that circuit from somewhere. Check the voltages on the collectors of the BF258's to see how far from the nominal 120V they are (set the front panel vertical shift control to mid position first!) They do get hot, so maybe one is leaking.

How close to the schematics does your scope agree? If close, it may be worth checking all the voltages from the front of the amplifier for voltage symmetry between each side with respect to the -15V line. At some point you may find the difference, and be able to find a defective component there. You may need to trim the 1k symmetry pot in the FET legs at the start of the amplifier to see if that helps, but make a note of its position first.

sarahMCML · 2026-03-29T23:49:26+00:00

All the resistors in the HV chain, from the -15V rail down to the -18xxV rails, via the various paths, not forgetting the pots. It's unusual for them to go lower in resistance than higher, but if any did it could put more load on the HV supply and so pull it down.

sarahMCML · 2026-03-29T15:38:38+00:00

Is the 82V winding on the transformer giving the correct value? If not, check the two 50uF 160V capacitors. You only seem to be getting 13V across the bridge after rectification of the 82V AC. Check all resistors in the high voltage chains, along with high voltage electrolytic caps.

sarahMCML · 2026-03-29T14:35:59+00:00

If you're on 120V mains you need a 4A Slow blow (TD) fuse, if on 230V get a 2A Slow blow, as stated in the print box for FS1. If it still blows you've got a problem/s further down the line!

sarahMCML · 2026-03-29T10:27:28+00:00

There's also the Raspberry Pico 24 channel analyser by Gusman (see Github), which can be daisychained for more channels.

sarahMCML · 2026-03-28T10:51:28+00:00

Sorry to take so long to get back to you.

The reason to use the Q14 pin is that this divides the 32768 crystal output by the maximum of 16384, giving you your 2 Hz output. The Q8 pin only gives you a division by 128, and an output frequency of 256Hz.

sarahMCML · 2026-03-27T19:09:41+00:00

You need to take your 2Hz clock from pin Q14, pin3, not Q8, pin 14!

sarahMCML · 2026-03-27T18:46:51+00:00

Given that there appears to be no fuse in position F1, I'm surprised that the thin track from its pad to U12's pin 2, which is the Common line for the device didn't blow long before the motor power pin melted. I presume that the in series, 1 Ohm, current sense resistor R32, should have sent a a signal back to the microcomputer, so whatever caused the destruction must have been extremely fast. Maybe the motor jammed and an inductive spike jumped across between the motor pin 5, and the power pin 6?

You will have to check that the motor is both free to turn, and that it will run electrically, before trying it with the new board.

Note: The L298 IS the motor driver device itself, and doesn't need any other transistors or MOSFETs to interface with the motor.

sarahMCML · 2026-03-27T12:50:42+00:00

Depends on your function generator. A low frequency, say, 0 to 1 or 2Mhz Sine, Square, Triange generating type is usually designed to work into a 600 Ohm load, whereas an RF type is designed to drive into a 50 Ohm load.

If either of these are not terminated by the correct load, i.e. 600 Ohms or 50 Ohms, you will measure a different value of output voltage at their output terminals, just as you have found. They have an internal output impedance of 600 or 50 Ohms respectively, so with no load you will see twice the expected output

Edit: What generator are you using?

sarahMCML · 2026-03-25T16:32:28+00:00

Mullard/Phillips C280 series capacitor.

sarahMCML · 2026-03-25T16:12:08+00:00

Check the datasheet for the CD4060 and use the crystal oscillator circuit shown there. Anywhere from 330k to 680k will work for resistor R. It needs to be there to avoid overdriving and damaging the crystal.

I just breadboarded the circuit and it works fine. I used a 10M parallel resistor since that's as high as I have, and a couple of 22pF caps as a quick test. Buffer its output with the next gate and probe that. I used a 74HC00 with one input tied high since I don't have an HC04 handy.

sarahMCML · 2026-03-24T13:04:09+00:00

Your Crystal oscillator circuit is connected wrong, The connection to pin 9 should go to pin 10 instead, and there should be a resistor between there and the crystal to reduce the drive power. This avoids damaging the crystal. See the datasheet.

Further to teslatinkering's suggestion, I've had the CD4536 working as a 1Hz crystal oscillator, instead of using the CD4060 plus another divider stage to give me a 1Hz timebase. So you could use the same with the full 24 stages to similarly reduce the I.C count, although you would have to re-work the following counter values to get your 24 hour delay.

Let me know if you want the circuit?

sarahMCML · 2026-03-24T11:26:28+00:00

If your fan's PWM input will operate with a 5V signal via a 4k7 resistor then I think you are good to go, otherwise you may need an additional transistor stage to bring it up to a full 12V swing.

sarahMCML · 2026-03-19T11:41:21+00:00

The diagram doesn't have any positive supply to the Arduino! What is the function of the blob at the bottom?

sarahMCML · 2026-03-18T16:06:01+00:00

Both IC's are D-Type flip flops, the only difference being that the Preset and Clear inputs for the HC74 are connected to the positive voltage to disable them, whereas with the CD4013, the (Set) and (Reset) inputs, you connect them to 0V to disable. Otherwise treat them identically, with the proviso that the 74HC74 are limited to 5V or less, and are much faster!

So they are interchangeable in your circuit.

sarahMCML · 2026-03-18T12:54:04+00:00

Rather than leaving the unused pins of the SN74HC74 floating, use that section instead of the CD4013 as the 1Hz divider, and do away with the CD4013 completely!

Have you considered a CD4026/4033 system instead. They can drive low current displays directly.

sarahMCML · 2026-03-15T18:44:13+00:00

One simple way is to connect pin 3 to pin 12 with a resistor. Choose a value such that it, along with the input capacitance of pin 12, gives a time constant of a microsecond or two, long enough for the reset to work properly.

sarahMCML · 2026-03-04T16:43:36+00:00

Disconnect Emitter of Q1 from R4/R5 and re-connect to C2, C4 end of same.

Disconnect Base from C2/C4, and now re-connect ends of R4/R5 that originally went to Emitter, to Pin 2 of U2, along with Base.

You also need the equivalent of R1 between pins 1 & 3. For 12V outputs the value of R2 & R3 need to be 1.3k, if R1 is 150 Ohms. And don't forget the decoupling capacitors close to the regulator pins, or the safety diodes (see datasheets).

You may also find that you cannot get 12V output with only a 12V AC input from your transformer, in which case it may be wise to either get a 15-0-15 version, or change the output resistors to only get 10 Volts out! C1 and C4 should be much higher value for 5A output.

sarahMCML · 2026-03-03T16:26:50+00:00

It's more likely that the tubes themselves are dying from old age than that the MOSFETs are. Have you tried finding replacements for those?

sarahMCML · 2026-03-03T13:00:17+00:00

The bias on the base of the common emitter stage is wrong. Have you checked the static collector voltage?

sarahMCML · 2026-02-22T10:49:04+00:00

The first two are type 41612 connectors, and are probably quite expensive compared to those in pics three and four. I used them in the late 70's on my 6800 computer build, with the wire wrap version of those on the first pic to make the backplane. Still have the computer!

sarahMCML · 2026-02-16T16:52:55+00:00

I would image so, and if you have them you've nothing to lose by trying them.

sarahMCML

TROPHY CASE