Any electrical engineers here?

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I picked up the following kit on eBay so I can practice soldering.

https://www.ebay.com/itm/Digital-Respond...=item3d50f3ab8e

Not surprisingly, all the instructions came in Chinese and are absolutely useless.

However the PCB was marked well and I'm reasonably certain I assembled it correctly. I am powering it with a single 6V A544 battery.

When powered on, the numerical display lights up with a value of 0. The buttons 1-8 don't seem to do anything, but the reset button does make the number 0 blink.


Any idea what the heck this thing is supposed to do?
 
Update - I used some spare bits to jump 2 pairs of contact points, and that seems to have gotten things a bit further.

Now, I can press each button to generate a number (1 through 8) on the display.. but that's about it.

Pics:

cd4511_1.jpg

cd4511_2.jpg
 
7448 IC? My senior class project used that, albeit with wirewrap.

A lot of the kits labeled as "for soldering practice" don't do much. the goal is to make something blink, and to... well, learn how to solder.

Now try out an SMT kit. Been a while since I've picked up an iron but 1206 & SOIC sized designs really aren't that bad. 0603 is tolerable, but smaller is painful & I don't think I could do a TSSOP anymore.

Now, on your kit, it looks like a buzzer of some sort. Does it beep when you hit a button?
 
It does beep when I press the buttons. The tone is slightly different between each button but hard to tell if it's that way intentionally.

As far as I can tell, the point of this kit is to make the IC display a number on the LCD.

I have to press the reset after each number or the LCD doesn't clear out.
 
Originally Posted By: Reddy45
It does beep when I press the buttons. The tone is slightly different between each button but hard to tell if it's that way intentionally.

As far as I can tell, the point of this kit is to make the IC display a number on the LCD.

I have to press the reset after each number or the LCD doesn't clear out.
I think you're right-something was definitely lost in translation to English in the listing.
 
Now, if you want to have fun, you can try looking up the p/n's on the parts. There seems to be too much stuff around the TO-92 (top left) for it to be a classic LM7805 (7805, etc) so I wouldn't be surprised if it was a zener regulated NPN (2N3904, 2N2222, 2N41??, etc). The IC looks like CD4511 which apparently has a latching function. You can google to your hearts content on it.

Don't expect long life out of the battery. Those red LED's are pulling probably 10mA per segment, and a 9V battery is all of 400-600mAhr. Well, it'll last a while but you get the idea.
 
Not an electrical engineer, but i miss the Heathkit days! I wish i still had the shortwave receiver i built as a teen.

I could kick myself for never buying Heathkits 2 channel AA_1800 stereo amplifier. 250 watts RMS with only .025thd.

But nowadays its all mp3 and phones, home stereo powerhouses are a thing of the past.
 
Last edited:
Originally Posted By: spasm3
Not and electrical engineer, but i miss the Heathkit days! I wish i still had the shortwave receiver i built as a teen.


Yeah, mass production sure killed the kit companies. Then again, I wouldn't be surprised if, if one adjusted for inflation, that the Heathkit might have been in excess of what one would pay for a fully assembled (and arguably more feature laden) radio today.

Example: SW-717 this shows production from '71 to '81, and a price of $90. If that $90 was in 1981 it would translate to $258 today, and if that $90 was for 1971 then it'd be $564 today.
 
That is all that a 7448 chip is supposed to do. It takes a number in binary and converts it to 7-segment output. Pressing the buttons produces a 4 bit number through the diodes.

http://www.ti.com/lit/ds/symlink/sn7447a.pdf

The 4511 is a slightly more modern version which adds a latch stage (basically 4 bits of RAM), so it is able remember the number that was last pressed, unless the power is cut off.

https://www.sparkfun.com/datasheets/IC/74HC4511.pdf

So what that board is doing, is all that it is capable of doing. And it must be correctly soldered.
 
Last edited:
Originally Posted By: supton
Originally Posted By: spasm3
Not and electrical engineer, but i miss the Heathkit days! I wish i still had the shortwave receiver i built as a teen.


Yeah, mass production sure killed the kit companies. Then again, I wouldn't be surprised if, if one adjusted for inflation, that the Heathkit might have been in excess of what one would pay for a fully assembled (and arguably more feature laden) radio today.

Example: SW-717 this shows production from '71 to '81, and a price of $90. If that $90 was in 1981 it would translate to $258 today, and if that $90 was for 1971 then it'd be $564 today.


maxresdefault.jpg

That is it! Thats the one i built!

My parents had no idea how dangerous my antenna was at the time( nor did I). I had a long wire run to our pasture fence. the pasture fence covered about 20 acres and was 6 strand. I had a long wire running from the pasture fence into my room hooked to that receiver. No lightning arresting of any kind. Lucky nothing bad happened. But i had fantastic reception at night!!!


Cost effective, probably not, but it was a lot of fun to build.
 
Last edited:
Originally Posted By: mk378
That is all that a 7448 chip is supposed to do. It takes a number in binary and converts it to 7-segment output. Pressing the buttons produces a 4 bit number through the diodes.

http://www.ti.com/lit/ds/symlink/sn7447a.pdf

The 4511 is a slightly more modern version which adds a latch stage (basically 4 bits of RAM), so it is able remember the number that was last pressed, unless the power is cut off.

https://www.sparkfun.com/datasheets/IC/74HC4511.pdf

So what that board is doing, is all that it is capable of doing. And it must be correctly soldered.


Right on then! Thanks for the explanation!

Not too bad for my first PCB solder project but I definitely need to buy some thinner solder as I made a mess with this one.
 
I just did a oscilloscope kit. Dso 150. Small resistors..I gave up trying to read the rating and just checked with multimeter. You might I that kit fun. Beware of fakes on eBay for that.
 
Originally Posted By: spasm3
Not an electrical engineer, but i miss the Heathkit days! I wish i still had the shortwave receiver i built as a teen.

I am an electrical engineer, but I'm hopeless around boards and soldering irons. I do remember an undergraduate project using breadboards though. I got pretty good at taking 1 ft bundles (sold at our department's supply guy) of phone cables and turning them into connectors. But other than that I suck at anything board related.
 
Originally Posted By: Reddy45
Originally Posted By: mk378
That is all that a 7448 chip is supposed to do. It takes a number in binary and converts it to 7-segment output. Pressing the buttons produces a 4 bit number through the diodes.

http://www.ti.com/lit/ds/symlink/sn7447a.pdf

The 4511 is a slightly more modern version which adds a latch stage (basically 4 bits of RAM), so it is able remember the number that was last pressed, unless the power is cut off.

https://www.sparkfun.com/datasheets/IC/74HC4511.pdf

So what that board is doing, is all that it is capable of doing. And it must be correctly soldered.


Right on then! Thanks for the explanation!

Not too bad for my first PCB solder project but I definitely need to buy some thinner solder as I made a mess with this one.

What do you use these days? I'm not much with a soldering iron, but I remember doing some project in junior high school using lead/tin solder to mechanically attach metal pieces. It wasn't for anything electronic. Then the next year I took a shop class, and the teacher demonstrated how to attach a metal handle to a metal cup. I had no idea what "flux" was until he showed it. When I tried it I got maybe one in 5 parts to adhere just based on sheer luck. I had no idea that the flux was supposed to prep the surface for the solder.

I do remember trying out a soldering iron once at work because I was kind of bored. We had some part that needed to get a resistor attached to work better, and it could be just soldered in place. I had no idea what I was doing, but I had a lot of time waiting for our prototypes to come back that I did it anyways.

Most of the electronics you get these days use RoHS compliant assembly, which means no more lead. I understand that a lot of solder joints aren't done correctly to account for non-lead solder.
 
Originally Posted By: y_p_w
Originally Posted By: Reddy45
Originally Posted By: mk378
That is all that a 7448 chip is supposed to do. It takes a number in binary and converts it to 7-segment output. Pressing the buttons produces a 4 bit number through the diodes.

http://www.ti.com/lit/ds/symlink/sn7447a.pdf

The 4511 is a slightly more modern version which adds a latch stage (basically 4 bits of RAM), so it is able remember the number that was last pressed, unless the power is cut off.

https://www.sparkfun.com/datasheets/IC/74HC4511.pdf

So what that board is doing, is all that it is capable of doing. And it must be correctly soldered.


Right on then! Thanks for the explanation!

Not too bad for my first PCB solder project but I definitely need to buy some thinner solder as I made a mess with this one.

What do you use these days? I'm not much with a soldering iron, but I remember doing some project in junior high school using lead/tin solder to mechanically attach metal pieces. It wasn't for anything electronic. Then the next year I took a shop class, and the teacher demonstrated how to attach a metal handle to a metal cup. I had no idea what "flux" was until he showed it. When I tried it I got maybe one in 5 parts to adhere just based on sheer luck. I had no idea that the flux was supposed to prep the surface for the solder.

I do remember trying out a soldering iron once at work because I was kind of bored. We had some part that needed to get a resistor attached to work better, and it could be just soldered in place. I had no idea what I was doing, but I had a lot of time waiting for our prototypes to come back that I did it anyways.

Most of the electronics you get these days use RoHS compliant assembly, which means no more lead. I understand that a lot of solder joints aren't done correctly to account for non-lead solder.


I use a $20 30 watt Craftsman pencil soldering iron and flux-core LEAD solder. Flows beautifully and makes strong joints!

I'm not really aiming to build anything in particular, but I occasionally need to use solder for appliance repair, and it's a great way to enhance your dexterity.
 
For more modern stuff, there's the Raspberry Pi 3 and also the Arduino. Lots of options with those.
 
Originally Posted By: Reddy45
Originally Posted By: y_p_w
Originally Posted By: Reddy45
Originally Posted By: mk378
That is all that a 7448 chip is supposed to do. It takes a number in binary and converts it to 7-segment output. Pressing the buttons produces a 4 bit number through the diodes.

http://www.ti.com/lit/ds/symlink/sn7447a.pdf

The 4511 is a slightly more modern version which adds a latch stage (basically 4 bits of RAM), so it is able remember the number that was last pressed, unless the power is cut off.

https://www.sparkfun.com/datasheets/IC/74HC4511.pdf

So what that board is doing, is all that it is capable of doing. And it must be correctly soldered.


Right on then! Thanks for the explanation!

Not too bad for my first PCB solder project but I definitely need to buy some thinner solder as I made a mess with this one.

What do you use these days? I'm not much with a soldering iron, but I remember doing some project in junior high school using lead/tin solder to mechanically attach metal pieces. It wasn't for anything electronic. Then the next year I took a shop class, and the teacher demonstrated how to attach a metal handle to a metal cup. I had no idea what "flux" was until he showed it. When I tried it I got maybe one in 5 parts to adhere just based on sheer luck. I had no idea that the flux was supposed to prep the surface for the solder.

I do remember trying out a soldering iron once at work because I was kind of bored. We had some part that needed to get a resistor attached to work better, and it could be just soldered in place. I had no idea what I was doing, but I had a lot of time waiting for our prototypes to come back that I did it anyways.

Most of the electronics you get these days use RoHS compliant assembly, which means no more lead. I understand that a lot of solder joints aren't done correctly to account for non-lead solder.


I use a $20 30 watt Craftsman pencil soldering iron and flux-core LEAD solder. Flows beautifully and makes strong joints!

I'm not really aiming to build anything in particular, but I occasionally need to use solder for appliance repair, and it's a great way to enhance your dexterity.

Mine was a Radio Shack soldering iron, but I was using 60/40 lead-tin solder. I don't remember the exact brand name (might have been Archer?) they used. I also only used the solder that came in the kit, but I'm pretty sure I would have had better results with rosin-core solder.

I managed to burn a bunch of tips, although the kit came with two spares. I didn't believe it, but they kind of just melted away.
 
OH yeah the tips on these cheap soldering irons don't last at all. I keep the very tip of mine tinned enough to work for the next time, but the rest of the iron is just corroded from heat.

I may actually pick up a rechargeable Hakko since the battery tech now gets them pretty dang hot and the lack of cords means no tripping/fire hazard.
 
Originally Posted By: supton
If that $90 was in 1981 it would translate to $258 today, and if that $90 was for 1971 then it'd be $564 today.


Oh, the silent, nefarious thief that is inflation... slowly but surely stealing all our meager fortunes. You mean to tell me that after my 3% raise I'm actually making LESS money than last year? Yessir.
frown.gif


Hand soldering is becoming a lost art, especially with SMDs. Good luck in your quest, buy a small amplifier kit and smoke it up to make yourself a little Bluetooth speaker for the back yard, and also brush up on woodworking skills. It'd be a fun weekend project!
 
I hate the fact that my eyes are getting old. Recently I goofed on a design and shifted the digital pins off by 1. I stripped some 22g wire to get one strand, and tacked it to a 32 pin QFN 5x5 package--that's 5mm on a side. Took a couple of tries but I finally got it. Then I used through hole parts to correct the mistake. I can't solder nicely but I can hack something into working.

I do refuse to do RoHS, although I suspect it wouldn't be so bad if I just used some flux and then washed the board afterward.

Several years ago irons like this, a Hakko 936 knockoff:
https://www.youtube.com/watch?v=WI2FyUfWPO4
popped up and I grabbed a couple. Seems to work fine for me. I haven't used enough to wear out a tip, but they seem quite nice.
 
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