Unknown IC - Page 1
Forum section: electronics / general

author: atunguyd
author_rank: Contributor
timestamp: December 24, 2014, 12:53:54 pm
content: Firstly let me say merry christmas and a happy new year to all on this board.Hi here is a christmas challenge for anyone.My wife has one of those christmas villages with the activity and lights, one activity is some ski lifts that move up and down, this has stopped working.I opened it up and the controller board for this has an IC blown as well as one NPN transistor. Problem is that the IS has no markings on it so I dont know what to use to replace it.I drew up the circuit and it is attached below. It is a very simple circuit so I am sure somone can make an educated guess as to what it is, I am thinking some sort of op-amp.The two switches are activated by the ski lifts when it gets to the end of it's travel, they are microswitches so they are only activated at the extremes of travel and during travel both will be open, thus I am thinking that this circuit must perform some sort of flip flop action with one switch detecting the lift at the top of it's travel and the other at the bottom of it's travel.Entire circuit runs off of 5V.Ignore the values within the IC, I just chose a generic 8 pin IC from eagle CADAny help would be appreciated.

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 24, 2014, 01:05:49 pm
content: Yes, it looks like a simple flip-flop that alternates the two outputs high/low or low/high. That would use the H-bridge to alternate the direction of rotation of the motor.

author: rob77
author_rank: Super Contributor
timestamp: December 24, 2014, 01:17:05 pm
content: definitely a RS flip-flop with complementary outputs. the two switches are the set and reset inputs.probably it would be faster to just replace it with a new circuit - the rest of the circuit is just a primitive H bridge, so no big dealwhat is the supply voltage ?i would go for a RS floip-flop made out of a comparator - e.g. LM393 goes from 2.0V supply up to 36V, it has 2 comparators in the package - use one of them for the RS flip-flop and the second one to act as a "inverter"it would be 1 x LM393 + approx 6 resistors (4 of them for the RS flip flop and 2 of them as pull-ups).random RS flip flop schematic from the net:

author: atunguyd
author_rank: Contributor
timestamp: December 24, 2014, 01:27:41 pm
content: Thanks Rob, that does look simple to use as a replacement, but if possible I would prefer to just replace the IC.I cant get my head around what it could be - the two outputs throws me.

author: dannyf
author_rank: Super Contributor
timestamp: December 24, 2014, 01:46:47 pm
content: Looks to be a full bridge driver. If the motions are not too complex, you have a chance to find a similar products. Otherwise, it is much easier to just duplicate its functionality, with a mcu for example.

author: rob77
author_rank: Super Contributor
timestamp: December 24, 2014, 02:55:09 pm
content: Quote from: atunguyd on December 24, 2014, 01:27:41 pmthis should work - see the attached whole circuit - includiong the part you're going to re-use ( H bridge drawn in a more conventional way ).R9-R12 and Q1-Q4 are your existing H-bridge.IC1A - R-S flip-flopIC1B - inverterthe values of the resistors are not critical at all - important is the ratio between them.R1:R2 = 1:3R2=R3=R4R7=R8and finally the pull-ups R5,R6 can be virtually anything between 470R and 10K - the LM393 can sink 16mA max, so don't go too low with the values of those ,1K is a safe value up to 12V supply.

author: amyk
author_rank: Super Contributor
timestamp: December 24, 2014, 03:48:20 pm
content: I wouldn't be surprised if it was a microcontroller. There are 8-pin single flip-flop ICs out there but none of them match.Not an AVR, but the 8-pin PIC12s match perfectly: Vdd on pin 1, Vss on pin 8, pin 4 active-low reset. 2, 3, 6, 7 being used as GPIOs. The 8-pin 68HC908s also match, and there are some other MCUs with similar pinouts e.g. P89LPC90x, but I'd bet on it being a PIC.

author: rob77
author_rank: Super Contributor
timestamp: December 24, 2014, 03:55:50 pm
content: Quote from: amyk on December 24, 2014, 03:48:20 pmmakes sense, but writing the software would require some time and you would need some tools to upload the code to the MCU. if someone has the tools and knowledge, then there is nothing simpler than replacing the stuff with a micro.

author: dannyf
author_rank: Super Contributor
timestamp: December 24, 2014, 05:27:10 pm
content: QuoteI would be surprised if it is (at least the genuine ones) - the toy market is dominated by those taiwanese mcu makers - mostly otp chips. Some of them do make PIC clones but for a toy maker to use a real PIC, s/he would be losing lots of money.

author: free_electron
author_rank: Super Contributor
timestamp: December 24, 2014, 06:16:27 pm
content: Could be a 555. You can use those as flipflop ..

author: rob77
author_rank: Super Contributor
timestamp: December 24, 2014, 07:43:12 pm
content: Quote from: free_electron on December 24, 2014, 06:16:27 pm555 doesn't have complementary outputs, i think it will be some kind of special flip-flop IC for toys (probably a modified 555) .

author: atunguyd
author_rank: Contributor
timestamp: December 24, 2014, 08:12:22 pm
content: Seems I got everyone scratching their heads ?Yeah a small AVR can easily replace it i guess. Are there PICs that dont need an external crystal? Because apart from the odd capacitor the circuit I drew above is all the components.Thanks for the circuit Rob. I will give it a go once Christmas is over. Next year my wife will have her village with the activity working. This year the lights alone will need to suffice.Sent from my GT-I9505 using Tapatalk

author: dannyf
author_rank: Super Contributor
timestamp: December 24, 2014, 08:54:08 pm
content: Most mcus today have internal rc oscillators. Actually, there are some mcus that do not have external crystals - some STM8L chips are like that for example.

author: SL4P
author_rank: Super Contributor
timestamp: December 24, 2014, 09:11:43 pm
content: Use any TTL/CMOS flip-flop or cross-wired inverters to get a bi-stable latch.One chip, drop in replacement (dead-bug style).15 minutes. $0.60c

author: amyk
author_rank: Super Contributor
timestamp: December 25, 2014, 02:25:05 am
content: Quote from: dannyf on December 24, 2014, 05:27:10 pmMicrochip are known to sell "genuine" imperfect devices under a different part number to manufacturers in China - look up CF745/CF775 for more info.

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: December 27, 2014, 02:21:29 pm
content: Microchip PIC12F675 would be perfect , same pawer pin 1 for VDD 8 for GND and MCLR in pin 4 so it meet exactly your circuit, you can write a simple program with Mikroc for PIC free for any firmware under 2k size, for such function it will take you 10 minute to do it all.