January 2019 – Eric Myers

YSC-4 Electronic Clock

Eric Myers Repairs, Soldering 18 Jan 201927 Sep 2023 0 Comment

I’ve just completed building a small electronic clock from a kit, the YSC-4 kit from HiLetgo, which I was able to purchase from Amazon for under $9.¹ My interest in this kit was to find something simple that is nevertheless good soldering practice for advanced beginners, and I was not disappointed.

Overview

The kit provides practice for a number of things that students should encounter:

an electrolytic capacitor (requires specific polarity)
a buzzer (also has specific polarity)
a transistor (three close leads, and requires proper orientation)
an IC socket, and the IC itself (oriented by a notch, and soldering close contacts)
segmented display digits (orientation and close contacts)
2 momentary contact switches (orientation)
a network resistor pack (orientation and close contacts)

This version comes with a wall-wart with USB socket and a USB cord to the power socket. I have since found a variation from another vendor (without the wall wart), which comes as a two-pack . Yet another version, which costs slightly less, has just terminal posts for the power, though I think students are more likely to use their creation if it has the USB power cord.

It took me under an hour to assemble, even with a break for a snack. A beginner might take longer, but would have no difficulty. The kit included a piece of paper with a list of components and a circuit diagram, along with (somewhat confusing) instructions on how to set the time and alarms. The kit did not include step-by-step assembly instructions, but since the PCB is well marked it is clear what goes where, and so step-by-step instructions really are not necessary. The one piece of advice to give to students is to start at the center of the board and work out, to make access to the leads easier when soldering.

Tips and Tricky Bits

Perhaps the trickiest thing in this kit was the orientation of the network array; it has a dot on one end and markings on the PCB to show which end goes where. We all missed that at first, so some boards had to have that component removed and resoldered. Another tricky point was the switches, because it was not clear at first without testing with a meter which contacts are always joined and which are only joined when the button is pressed. Rotating the switches by 90 degrees will be the same as having the buttons always pressed down. As you might be able to see from the photo, the leads go on the sides, not the top and bottom. It helps to think of the leads as two sets of flat straps that go across the switch from one side to the other.

Another thing that might trip up beginners is the orientation of the segmented display (the decimal points go at the bottom, as does the writing on the bottom side). Unlike other PCB’s I have worked with, there are no components where you have to guess the orientation

Some other things to note:

This clock has a 24 hour display (no 12 hour display).
It will chime 3 times on the hour (unless you turn that off).
There are two alarms. When initially turned on, the time is 12:59 and the two alarms are enabled and set to 13:01 and 13:02.
There is no back-up battery, so you have to set the time (and alarms) again if you ever unplug it or it looses power somehow.

The display is very bright, but since the segments in the segmented display are white when not lit it can be hard to read the time from the bare clock face. You can see this in the photo at the top of this post. The solution to this is to cover the display with red or grey tinted plastic, so that only the lit red segments are visible. I had a roll of red “tail light repair” tape which is 2″ wide and it fit perfectly, as shown here:

YSZ-4 clock with red tape over the display

However, we’ve learned not to put the tape on the display until the clock is working, as it obscures the decimal points at the bottom, leading to more problems with the display ending up upside-down.

We have had some success with replacing the buzzer with an LED, though it seems that the LED may eventually burn out, so it might be wise to add a resistor in series. One student tried to put an LED in parallel with the buzzer, and that failed, but again maybe adding a resistor would make it work (that has not yet been tried).

Operating Instructions

The operating instructions that came with the kit are written in English, but appear to be a direct translation from Chinese and are somewhat confusing. I found another set of instructions on the net that are also Chinese written in English, but differently. From those and my own experience I was able to put together these operating instructions:

Switch S1 (on the left) is the Menu button. An initial long press enters the first menu. The menu pages are named A, B, C, D, E, etc., and the menu letter is shown in the first digit of the display. A short press on S1 takes you to the next menu. You can only exit the menus by stepping through all of them; a long press will make them step through quickly (but if you don’t remove pressure at the right time you’ll start the menu list over again).

In each menu, switch S2 (on the right) is the toggle/increment button. On each menu page, us it to toggle a feature on or off, or to increment a numerical value. For numerical values you can hold the button down and the count will go up automatically.

The menu pages are:

A – Hours, from 00 to 24 (there is no 12 hour option)
B – Minutes, from 00 to 59
C – Hourly chime. If enabled the clock will beep 3 times on the hour, but only between 08:00 and 20:00.
D – First Alarm on/off
E – First Alarm hour
F – First Alarm minutes
G – Second Alarm on/off
H – Second Alarm hour
I – Second Alarm minute

If an alarm is turned off then the menu will skip the hour and minutes items for that alarm. There is no way to exit the menu pages early; you must cycle through all of them to get back to normal operation.

Outside of the menus, a short press on switch S2 will change between displaying hours and minutes or displaying minutes and seconds. While the minutes and seconds are displayed, a long press on S2 will reset the seconds to zero, and then a short press on S2 will start the clock again from 00.

When an alarm is sounding there is no way to turn it off. You just have to wait for it to finish.

Co-Curricular Transcript

Students at SUNY New Paltz can participate in a 4-Step training program in electronics soldering, where construction of this clock is the 4th step. Once the clock is shown to work they can a certification added to their co-curricular transcript. The student must request this certification; the instructor cannot give it without a request.

To request certification go to my.newpaltz.edu and click on “Student Engagement” in the main menu. Then click on Co-Curricular Transcript in the Student Engagement menu. In the search form enter “solder” in the Keyword field and press “Search.” Click on the item and fill in the form.

3D Printed Case

Students can have a case for the clock 3D-Printed at our Hudson Valley Additive Manufacturing Center. Payment must be made by credit or debit card after you submit the STL file. The cost is around $1.30. Under the “Resources” menu on the HVAMC page open the “Submit a Build” item and click on “Students”. The STL file describing the case is YSZ-4_ClockCase.stl, but it will have to be renamed for submission (see the instructions on the submission form). It was created with OpenSCAD.

More info…

The chip used in this kit is an Atmel AT89C2051 micro-controller, which is capable of much more than just being a clock. The vendor (or someone) must have flashed the IC with a simple clock program for this kit. Maybe it would be possible to re-flash it to allow for 12 hour mode. Anybody up for this challenge?

Also, I tried powering it with a single 3.2 Volt coin battery, and that worked initially, but drained the battery very quickly, so it’s not really a viable option.

These instructions by clobber24 on Instructables for a C51 4-Bit Clock apply, except for the power jack. That page also links to 3D printed cases. He printed a battery case for three AAA batteries, which he says worked, but he does not report on battery life.

Notes

in 2019. The cost is slightly higher now. ↩

Welding Ventilation Estimate

Eric Myers Buildings 9 Jan 201913 Jan 2019 0 Comment

I have been investigating the requirements for students to be able to weld on campus, which is needed for our Baja SAE team, for projects for our Engineering Senior Design course, and for other various engineering projects. One of the requirements is, naturally, adequate ventilation. Specifically¹

Adequate ventilation providing 20 air changes per hour, such as a suction hood system should be provided to the work area.

We have considered several shop rooms as a possible welding space, but it’s not clear if they already have sufficient ventilation or what it would take to add enough ventilation capacity. What I realized today is that it is useful to turn the question around and ask: for a “standard” amount of ventilation, how big a space can be properly ventilated to obtain 20 air changes per hour?

What is a “standard” unit of ventilation? I have a regular old box fan in my lab, and I was able to measure the speed of the exiting air using a borrowed anemometer. Fans like this are ubiquitous on a college campus, so I’ll chose that as the standard. The dimension are 19″ × 18.5″, for a total area of 2.44 square feet. I could compute the flow rate (volume/time) by multiplying the area by the speed of the air exiting the fan (in the same linear units!), but this anemometer was so smart that if I enter the area it automatically gives me the flow rate in cubic feet per minute (CFM). The flow rate varied with position around the fan, so I took what seemed like a representative average of measurements all over (we could do this better, but I just need a ball-park estimate). There are three speeds: low, medium, and high. The results were:

Low: 1750 CFM,   Medium: 2250 CFM,   High: 2650 CFM

Just to use a rough order-of-magnitude estimate I will use 2000 CFM in what follows (mostly).

Next, I need a unit of volume. One of the rooms that is being considered for welding is room 008 in the basement of Resnick Hall (RH 008). That room has a roll-up door which happens to be exactly 8 feet wide and 8 feet tall. I need a unit of volume, not area, so I’ll imagine a cube that goes 8 feet back from that door, for a total of 8’× 8′ × 8′ = 512 cubic feet. This is about the size of the smallest PODS storage container, so I will call this a “pod”² (their container is actually 8′ × 7′ × 7, but this is close enough for our estimate).

The questions then are 1) how many “pods” can a single box fan ventilate (at 20 air changes per hour), and 2) how many pods does it take to match the volume of the room in question? If the numbers are wildly mis-matched then we know we can stop there. If they are close, then we can refine our calculations, or just make sure we add an “engineering margin” to be sure we are over the required capacity.

First, how many “pods” can a single box fan ventilate? Let’s call that unknown N, and compute it by setting the required ventilation rate equal to the measured rate:

On the left we have the required flow rate for 20 times the volume of N pods (in cubic feet) every 60 minutes. On the right we have a representative flow rate for a box fan, in cubic feet per minute. I’ve taken care to use the same units everywhere for time and volume. Setting these equal and solving for N gives:

The numerical value comes out to be 11.718, which I will round up to 12 pods. (Using 2250 CFM for the “Medium” setting on the fan would give 13 pods.)

But I have to take into account that the ceilings in RH 008 are rather high. They are certainly more than 8 feet, probably more than 12 feet, and maybe even 16 feet. Since this is only an estimate, I’m happy to perhaps go over a bit and guess 16 foot ceilings, which means we have to imagine two of these pods stacked on top of each other. Then the corresponding floor area we can ventilate with one box fan ends up being half the number, or 6 pod “footprints” of 8′ by 8′.

If the floor area of RH 008 is about the same as 6 of these 8′ by 8′ pods, then we are okay with just one box fan. If it’s twice as large, then we can use two box fans. If it’s as much as as four times this then we could put 4 box fans across the bottom of the sliding door and have enough ventilation.

If we need multiple box fans across the opening then I imagine they might be in a frame, perhaps with wheels to make it easier to move in and out of place. The box fans are 19″ wide, and with some allowance for the frame that means we could get as many as 4 across the opening. That would cover 4×6 = 24 pod “footprints”.

And note that the estimated 2000 CFM for one box fan was closest to (and under) the “Medium” setting. We can easily re-work this estimate with the fan(s) set on “High” if needed. This will give us an estimate for the upper bound of possibility. Using 4 box fans set to “High” at 2500 CFM would give 24 × 2500/2000 = 30 pod footprints.

My purpose here was to make an estimate to see if we could use one or a few box fans to ventilate a particular room, but the method can easily be applied to any other room, because a box fan provides a reasonable standard of ventilation, and a “pod” of 8’× 8′ × 8′ or with a footprint of 8’× 8′ is a representative unit of volume which one can easily picture in any room – no tape measure required. We can use this to quickly rule in or out the possibility of ventilating any candidate space.

See https://www.newpaltz.edu/ehs/safety_welding.html . ↩
Though I want to be clear that I am not offering any product or service which competes with those of the PODS company, so I hope they don’t sue me the way they did U-Haul in 2012. ↩

Wooster Hall Rooftop Mystery

Eric Myers Astronomical, Buildings 7 Jan 20198 Jan 2019 0 Comment

A few weeks ago I visited Wooster Hall with a time-lapse camera to try to see what happens to the light from the skylight over the main staircase at solar noon on the Winter Solstice. I was a few days early, but even so, I think I uncovered the basic idea, which you can review in a previous blog post.

The result is that the four columns of light that appear at the bottom of the staircase on the equinoxes now appear on the slanted ceiling near the skylight, and don’t extend down any further. Here’s a picture (click on it for a bigger view):

But as you will notice, there appears to be something in the way, preventing the columns of light from extending all the way downward, especially on the left. What could that be? In the original post of the video I mused that perhaps there is something on the roof which is casting a shadow. Looking at the roof from a nearby building I could see that there are vents on the roof that are near that skylight. And after that post I heard from the building architect that those vents are necessary to remove smoke in the event of a fire. It’s doubtful they could be moved. But from that viewpoint I wasn’t sure that these were actually in line with the skylight, and I’m still doubtful that they are the culprit.

Someone else suggested that I could see what is on the roof using Google Maps. That turned out to be very helpful. Here’s the view from directly above, with some added markings (click on the image for a bigger view):

The skylight is circled in red, and the green line shows my line of sight from the Chemistry building to the Wooster roof. As indicated by the compass needle at the right edge, vertical on this photo is North, and as you might expect the four openings in the skylight line up with North, rather than with the building. You can also see the vents near the skylight, the sort-of round things that are to the right and below the skylight. But note that they are NOT directly below (i.e. South of) the skylight. This means that they cannot be blocking the light in the way seen in the videos! Which is what I suspected when viewing them from the Chemistry building.

So what is blocking the light? I’m going to guess that it’s the roof itself — actually a wall which is a part of the roof. As you can see from the photo, the roof has several levels (it’s easier to see this from the side view from the other building). The part of the roof where the skylight is located is higher than the roof farther to the south, and there is a wall dividing the two levels. You can see this a little better if we zoom in (again, click on the picture to make it (somewhat) larger):

Wooster Hall from above, showing the wall south of the skylight.

The orange line shows the position of the wall, which I suspect is just high enough to block the lower part of the skylight when the sun is at its lowest in the sky, on the Winter Solstice. If you go back to the picture of the skylight from the inside, it looks like whatever is casting the shadow is larger on the left and sloping down to the right. But keep in mind that the building is turned away from North, and the skylight image is cast on a slanted ceiling/wall (which might even be curved). My guess is that the shadow is actually a horizontal line, caused by the wall on the roof.

And, by the way, if you don’t see that the orange line marks the position of a wall, then go to Google Maps yourself and find this building and select the “satellite” view. The way Google presents the images they actually change your view slightly as you drag the map, giving a sense of 3D which shows more clearly that the roof has multiple levels. It’s pretty cool that they can do this without your having to wear 3D glasses.

Is there anything we can do to unblock the sun? Well, at least it’s not a vent that’s required for fire safety, but the wall is probably necessary too. Maybe a section of the wall could be replaced with an open railing or chain-link fence which would still provide safety to whoever is working up there, but would let the light through to the entire skylight at the Winter Solstice. Or maybe not.

I still want to get up on the roof to try to confirm this conjecture. By measuring the distance of the bottom of the skylight to the base of the wall, along with the height of the wall, I could determine the position of the shadow of the wall for a given elevation of the sun, and verify that the shadow would reach the skylight. And maybe figure out how much the wall would have to be lowered (instead of completely removed). This isn’t over yet, so stay tuned…

Winter Solstice in Wooster Hall

Eric Myers Astronomical, Buildings 2 Jan 20198 Jan 2019 0 Comment

Wooster Hall at SUNY New Paltz has a neat feature: the main staircase is aligned directly North/South, and skylights are positioned above it so that at solar noon on the equinoxes the bottom of the staircase is illuminated by four columns of light which crawl slowly across the floor. It’s an exciting event on campus, for some reason. This past spring I made a crude time-lapse video of this. Also, on the summer solstice, and again at solar noon, the upper part of the staircase is illuminated. I made a much better time-lapse video this time, which includes a demonstration of the reason for the change in the sun’s elevation, where I’m assisted by my 9-year old daughter, Amanda.

But what about the Winter Solstice? There are no markings on the staircase or nearby, and in any case the sun is so low in the sky in winter that it’s not clear that there would be anything to see. But since I’m always curious about such things, I decided I had to find out.

The weather for December 21st was expected to be overcast and rainy, so I actually visited Wooster hall earlier in the week, on two different days. First, on Tuesday, December 18th, I was able to get the general idea of what’s going on:

As you can see, the four columns of light from the skylights move across the wall directly below the skylight, but they don’t extend further down.

It seemed like I had gotten there a little bit late, so I came back earlier the following day. This time I think I got the whole thing:

There is a jump at the very beginning of the video, where I repositioned the camera. Unfortunately, I moved the camera closer to some lights on the wall, and it looks like that changed the contrast of the video and made everything darker. Even so, you can see the whole event as the sun crosses over.

Both of these time-lapse videos were created using a very nice piece of software called TLDF (which stands for “Time-Lapse-De-Flicker). Actually, I just used the free “lite” version for Mac, called TLDFLITE, and that worked fine for this project. You can find out more about it at https://timelapsedeflicker.com/

One thing that’s very obvious from both videos is that there are not four full bars of light, the way there are at the summer solstice and the equinoxes. There is a curved shadow that blocks the light, mainly on the left side, curving down to the right. It’s probably something on the roof near the skylight, but I don’t quite know what. I went to the top floor of the nearby Chemistry building to get a view of the roof of Wooster Hall, and I can see that there are ventilation stacks near the skylight which might explain the shadow, but I wasn’t sure either of them lined up quite right.

So now I want to get up on the roof to see what is in the way, and to see if perhaps it can be moved out of the way. If I can’t get up on the roof, then perhaps I can find someone with a drone to help inspect that area. Stay tuned….