ID an IC in a ceiling fan receiver/controller - Page 1
Forum section: electronics / projects

author: bobdring
author_rank: Contributor
timestamp: December 21, 2017, 06:57:24 am
content: Hi,I'm Trying to repair a elderly Omega RF remote controlled ceiling fan.I have two of these fans but the faulty one just creeps around then stops.Checked google for a circuit of the RHINE UC7051R pcb but no luck, so decided to reverse engineer it.First problem is that I can't find any info on the receiver/fan control IC and I need your help.The IC is marked RH7050 and it is in a DIP20 package with no manufacturers logo.Pin 3,4,5 & 6 are the remotes 4 bit ID dip switch input.The mating transmitter IC is a Holtek HT12E in DIP18 if that helps at all. The mystery IC is not the mating HT12D as that is a DIP18.Can anyone help me find data on the RH7050 ?Bob

author: SeanB
author_rank: Super Contributor
timestamp: December 21, 2017, 07:40:12 am
content: Creeping round then stops says the capacitor on the motor is low in value, or the bearings are gummed up with polymerised oil. The capacitor will be a 2uF 400VAC polycarbonate unit, soldered to the board or next to the motor.

author: bobdring
author_rank: Contributor
timestamp: December 21, 2017, 12:26:59 pm
content: Hi SeanB,Thanks for your interest.There are 3 big caps. A 1.75uF and a dual 1.75uF / 3.5uF. They measure OK with my DMM and the bearings are OK.I will pull the caps and check them for ESR too. I think the caps are switched in by 3 triacs, a failure there might give the same symptoms.There is also a relay for (reversing?) and another triac for the light dimmer. The radio circuit is under a tin shield.As for the IC I have never had a web search fail before, except for custom parts. Possibly its a house number of some other part but someone might know a good number to use instead. The date code says 1992 so pre PDFs. 20 pin Dip...I would replace the fan but I have others of the same age and so reverse engineering would be worth the effort.Also retirement money is a bit tight.Bob

author: SeanB
author_rank: Super Contributor
timestamp: December 21, 2017, 01:22:43 pm
content: How did you test them, they normally go low in capacitance, or start to break down internally. The 1.75uF one is likely the power supply capacitor, the dual unit will be the one used to give the phase shift for the shaded pole motor, and is switched to give the speeds. If the single capacitor is low capacitance the motor will start up but the controller will lose power.Also check the electrolytic capacitors on the board, there will be a power supply that is 100-470uF around 16V or so, and if it is low the same symptom.Photo of the board will help as well

author: bobdring
author_rank: Contributor
timestamp: December 21, 2017, 01:52:43 pm
content: SeanB,I measured the caps differently.The dual one out of circuit with the DMM on capacitance. IT is a 3 pin PCB mount.The other in circuit again with the DMM. The caps has wires that are hot melt glued to PCB and componentsHow would you test them?The power for the 90mm round donut style PCB comes from a tiny PCB mounted transformer approx 30mm squareThe motor has 4 wires.I will set up the camera tomorrow.Bob

author: amyk
author_rank: Super Contributor
timestamp: December 21, 2017, 05:32:17 pm
content: What about the other pins? HT12D is available in a 20-pin (but not DIP) package, and there are others with very similar pinouts like SC5272.

author: bobdring
author_rank: Contributor
timestamp: December 21, 2017, 11:51:41 pm
content: amykI think that the RH7050 is made by the Rhine electronic co Taiwan but still can't find any data.I looked up the the suggestion but can't find anything that matches. Some 20 pin DIPs but they have no connections to pin 10 & 11 and my PCB definitely does.I have attached some photos as promised.

author: bobdring
author_rank: Contributor
timestamp: January 02, 2018, 09:47:32 am
content: Well, I traced out the circuit and connected the fan motor directly to the mains (No PCB) with the caps in circuit the motor runs OK when connected for High, Medium and low speed. So that rules out faults in the motor and the caps.U2 RH7050 connectionspin-signal1 GND2 GND3 S1-1 REMOTE ADDRESS4 S1-2 REMOTE ADDRESS5 S1-3 REMOTE ADDRESS6 S1-4 REMOTE ADDRESS7 GND8 R27-19 R27-210 U1-1 OUT (U1 is a LM324 opamp) The signal is a digital bit stream from the RF receiver section11 *fan low R17-112 *fan medium R18-1 R19-113 *fan high R20-114 R22-1 C11+V15 R22-216 summer/winter relay driver R21-217 +5V / ACTIVE R23-218 R23-1 C23-2 LINK R36-219 *lamp R24-120 C13-2 R25-1*These pins are buffered by NPN transistors that then drive TRIACswhen I have the fan controller repaired I will do a proper circuit diagram

author: bobdring
author_rank: Contributor
timestamp: January 06, 2018, 06:44:45 am
content: The main difference between the RH7050 and the HT-12D apart from the extra pins is that the RH7050 also controls dimming the light on the fan. While I have now worked out the purpose of the main IC pins, finding a data sheet and a vendor are still proving difficult. Has anyone found a similar IC in a fan but with perhaps different markings?

author: bobdring
author_rank: Contributor
timestamp: January 15, 2018, 08:13:03 am
content: A little bit more info about the fans remote serial protocol.It uses the standard Holtek HT-12E IC in the transmitter but instead of the standard 12 bit protocol of 8 address bits and 4 data bits (4 buttons) the button wiring has been modified to support 6 buttons by using three of the address bits as data. This scheme would not work with the standard HT-12D receive decoder but it suits the custom RH7050 decoder.more detail is attached.

author: bobdring
author_rank: Contributor
timestamp: January 19, 2018, 11:39:21 am
content: Since I'm now reverse engineering the fan controller.I have started a new topic with a title that hopefully will allow searchers to find it.https://www.eevblog.com/forum/projects/rhine-uc7051r-ceiling-fan-remote-receiver-reverse-engineer/msg1404415/#msg1404415