What's the use of this thing - Page 1
Forum section: electronics / beginners

author: Ahura Mazda
author_rank: Contributor
timestamp: October 10, 2020, 10:21:05 pm
content: So, I've acquired this device and I don't understand what it's purpose is.Upon inspection, all there is is linear transformer, outputting 100 Vpp when supplied from 240Vac, coming to bridge rectifier. When no buttons are pressed, output is low. When one button is pressed, output is non-inverted rectified signal, and inverted when only second button is pressed. Resistors in series with LED just to notify when button is pressed. That's it.Now, I don't understand why such device exists since there's output signal only if button is pressed, and I mean, you have to hold it if you need signal for longer(?). I can only assume it is for some testing of sorts where you want to pulse the signal as you need, but what could that device be?I would like to be enlightened, and would appreciate suggestion from much more experienced people here. Thank you.

author: rsjsouza
author_rank: Super Contributor
timestamp: October 10, 2020, 10:34:12 pm
content: Well, seeing it is a full custom piece of equipment, it was probably designed and assembled to fit a specific purpose - i.e., someone saw a need for a pulser or a momentary supply and assembled something.If I understood its operation correctly, I could see this for educational purposes to show how a diode or a bridge rectifier works - i.e., showcasing what happens when a "positive" or a "negative" voltage is applied to it.

author: hexreader
author_rank: Frequent Contributor
timestamp: October 10, 2020, 11:05:17 pm
content: Here is what I see:Mains input through switch and fuse to transformer primaryTransformer will reduce mains AC voltage to lower AC voltage (no markings so no idea what voltage, but 100 Volts pp equates to about 35 Volts RMS)Secondary of transformer goes to bridge rectifier, which converts AC to DCTwo switches seem to select full-wave or half wave judging by your description- possibly a resistor switched in or out for high/low current - hard to saySeems to be a flying lead going no-where. Did it fall off?There are two power terminals red and black. Anybody's guess what they supplied. Some kind of low power medium voltage device.As for it's usefulness now.... You could remove the switches and wire the bridge rectifier output directly to the red and black terminals for a DC power supply. You might even fit an electrolytic capacitor for a smoothed DC supply.Avoid touching mains wires at all costs. - This gadget is dangerous. Even 100 Volt p-p can be scaryIf you do not know what you are doing - best just bin the whole thing. It would make a horrible DC supply anyway, and if you do not know what you are doing, it could easily destroy anything that you connect to it.If you can read any markings on the transformer or resistors then someone may give more detail.Can't think of any modern use for a 35 volt unsmoothed supply35 Volts is average full load value - unloaded voltage may be a good bit higher - my calculations could be wrongEDIT: are there any marking on the bridge rectifier? + - ~ ~ ?Can you draw a wiring diagram? or give clearer pictures of the two switches and 3 LEDs?After more thought, The post below from Paul Rose makes a lot of sense

author: Paul Rose
author_rank: Regular Contributor
timestamp: October 10, 2020, 11:18:42 pm
content: Having trouble tracing the full thing from the pictures.What are the front switches? SPDT, but momentary and pushbutton?And it isn't clear what one of the output terminals is connected to (wire goes off picture).But if it is as you say, momentary pulsing DC positive or negative (depending on which button), then it could be a crude directional control for a DC motor? One button for clockwise, one for counterclockwise?Maybe a Ham radio operator used it to rotate an antenna mast?

author: Ahura Mazda
author_rank: Contributor
timestamp: October 10, 2020, 11:28:37 pm
content: No worries, I'm aware what I'm doing.QuoteTrue, I was thinking of the same thing since this seems useless for now. It's quite nice voltage, definitely higher than of any transformers I have.QuoteYeah, I'll do that now.

author: Ahura Mazda
author_rank: Contributor
timestamp: October 11, 2020, 12:23:23 am
content: So, this is the diagram. Pretty straightforward. Both off, outputs on high, one on, (non)inverted signal on the output.

author: Paul Rose
author_rank: Regular Contributor
timestamp: October 11, 2020, 12:45:04 am
content: Yes. Still think some kind of DC motor direction control where you only want the motor to turn while you are holding the button (while you are paying attention).The motor would not care about the rectified but unfiltered DC.Code:Buttons : OutputsOFF,OFF = +,+ (zero difference)OFF,ON = +,- (positive difference)ON ,OFF = -,+ (negative difference)ON ,ON = -,- (zero difference)

author: LA7SJA
author_rank: Regular Contributor
timestamp: October 15, 2020, 05:45:57 am
content: This could be an antenna rotator kontroller boks? 48VDc motor rotating the antenna, it could also be used to tune a vacum capacitor on a large magnetic loop antenna 160M/80M. In both cases the motor/gearbox have an endpoint switch with a diode to stop the movement one way and only let it go in the opposit direction once the end is met. The thing looks to be a one off, hand made in ham style (use whatever you have laying about).LA7SJA