Help understanding a circuit. - Page 1
Forum section: electronics / beginners

author: carlosinseattle
author_rank: Contributor
timestamp: September 25, 2019, 05:08:26 am
content: My 2nd post since discovering the site a couple years ago.Can someone help me understand what this circuit does? I think it's called an RC circuit. But what I want to know is what purpose does it serve.

author: james_s
author_rank: Super Contributor
timestamp: September 25, 2019, 05:21:47 am
content: What is it in? That looks like a filter of some sort.

author: Zero999
author_rank: Super Contributor
timestamp: September 25, 2019, 09:34:44 am
content: Are you sure the bluish green components are not inductors, rather than resistors? Compare the value read using a multemeter, with the one obtained by reading the colour code.

author: carlosinseattle
author_rank: Contributor
timestamp: September 26, 2019, 04:08:59 pm
content: Quote from: Zero999 on September 25, 2019, 09:34:44 amI am not sure at all whether it's a resistor or inductor. I don't know how to test for the difference, but I'll read up on it and try to test this evening. Here's a closer picture if that helps.

author: carlosinseattle
author_rank: Contributor
timestamp: September 26, 2019, 04:11:25 pm
content: This is for a German made slot car track. It's fed by a 14 volt .5 amp DC power supply. The circuit pictured is connected to the positive and negative wires.

author: RoGeorge
author_rank: Super Contributor
timestamp: September 26, 2019, 04:47:17 pm
content: Probably a filter to reduce the unwanted/parasitic radio frequency waves created by the power tracks while the cars are running.

author: AVGresponding
author_rank: Super Contributor
timestamp: September 26, 2019, 05:42:27 pm
content: If they were resistors, that'd be 6R2 each, so 12R4 in total, which would allow a bit over an amp on short, but that would be the best part of 20w...

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 26, 2019, 06:26:14 pm
content: I'd say 6.2 uH inductor.

author: carlosinseattle
author_rank: Contributor
timestamp: September 26, 2019, 11:48:38 pm
content: I posted this question in another section, the question above is related and part of the whole project.I'd like some advice and help with understanding a how this whole system works, possible reverse engineering it, and then trying to adapt it for a related use. It's for toy slot cars and this is way out of the area of expertise for slot car enthusiast. I'll list what I'm trying to do and I'm open to any and all suggestions.How does a little converter box work? It converts DC to 50hz "pulsed" DC powerThe box was used on German slot car sets from the early 80's to late 90's only.Why can't a regular dc motor "see/recognize" a 50hz pulsed dc signal?Since the boxes are in short supply I'd like help to recreate it, the cheaper the better:)I'd love for somebody to hold my hand through this and if I'm trying to do something stupid or impossible i'd love to know sooner than later, before i wast too much time. I can provide more details and pictures if somebody is willing to help, I just didn't want to post a bunch of information only to be told this isn't the correct place on the forum.

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: September 27, 2019, 07:15:10 am
content: carlos,would this help?http://slotbaer.de/index.html

author: AVGresponding
author_rank: Super Contributor
timestamp: September 27, 2019, 01:08:34 pm
content: Well, the components in the pics you uploaded are definitely going to be to filter out interference.The DC resistance of those inductors will be very small, you'll not even be able to get a meaningful measurement with an ordinary multimeter.I see no reason why DC motors won't work here. By 'pulsed DC' it almost certainly means half or full wave rectification but without any smoothing, so no bulk capacitance.Speed control is likely by a wirewound rheostat in the handheld controllers.If the motor you want to use doesn't work, it may simply be inappropriately rated for the voltage or current the 'black box' delivers.I can't imagine a toy from this era having anything as sophisticated as PWM.

author: Zero999
author_rank: Super Contributor
timestamp: September 27, 2019, 01:17:30 pm
content: Quote from: carlosinseattle on September 26, 2019, 04:08:59 pmThe colour bands are blue (6), red (2) and gold (×0.1), silver (10% tolerance) which would give 62×0.1 Ω = 6.2Ω 10% tolerance, if it's a resistor, so is the value you'd get by measuring it with a multimeter set to resistance mode.https://www.digikey.co.uk/en/resources/conversion-calculators/conversion-calculator-resistor-color-code-4-bandIf it's an inductor, then the value measured by the meter will be significantly different, probably much less in this case. As mentioned above, it's most likely a 6.2µH inductor.