"Stealing" power from HP LaserJet - Page 1
Forum section: electronics / general

author: RiverTown
author_rank: Regular Contributor
timestamp: March 24, 2016, 01:07:19 pm
content: Hi,I have HP LaserJet 4000TN printer that is connected to network wirelessly.I've used this modulehttp://www.ebay.com/itm/301262260623?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITas wireless client bridge to achieve wireless connection (yes it was pain in the ass to adjust).Now I'm searching a way to steal some power from printer for powering the module, preferably without opening a printer. I don't want to have another cable just for a 5V supply.Module takes 5V, and 500mA according to specifications.There are Paralel port, RS-232, accessory port (Jet Assist), and outputs of JetDirect J3111A card (BNC for Thinlan, use RJ-45, and LocalTalk port) at the back of the printer.I think that accessory port is my best bet but I can't find any informations about it, and I lost more than day searching. Nor did I find pinout, nor specifications. I didn't even able to find service manual of accessories some that uses this port, so that I can reverse engineer it.Does anybody know more about this port, or have some other advice how to steal 5V at 500mA from this printer?

author: XOIIO
author_rank: Super Contributor
timestamp: March 24, 2016, 01:13:33 pm
content: Well, depending on the connection, you could make something which sits in between the printer and the wall plug with a 5v power supply in between, if the issue is being short on wall plugs.Aside from that, don't really think there is any way to do it without getting inside the thing to the power supply, I can't even really ind anything mentioning a jet assist/accesory port.

author: Shock
author_rank: Super Contributor
timestamp: March 24, 2016, 01:29:12 pm
content: Use a usb port at the back.

author: RiverTown
author_rank: Regular Contributor
timestamp: March 24, 2016, 01:52:25 pm
content: Quote from: XOIIO on March 24, 2016, 01:13:33 pmYes, that is my last option...Everything I could find related to accessory (HP JetDirect) port was from brochures, and user manuals for different LaserJet models. There was no technical data. I had a go with a multimeter and measured 3.3V, 5V (4.7V) on some pins, and find ground pins. But I don't know purpose of that pins, nor current ratings.This is an old printer, and doesen't have USB port at the back.

author: German_EE
author_rank: Super Contributor
timestamp: March 24, 2016, 09:09:19 pm
content: Look around and see of there is an extra socket for a second paper feeder. I have a Brother printer that has a DIN socket on the back intended to connect to a second sheet feeder and one pin is at 24V. One DC-DC converter later and my router/USB Printer Driver has a power supply.

author: tautech
author_rank: Super Contributor
timestamp: March 24, 2016, 09:19:21 pm
content: Does this printer have a Duplex option, if so you you could likely find a sufficiently capable outlet that supplies it.If the voltage is too high, a simple 317 or 7805 circuit will give you the 5V you need.

author: German_EE
author_rank: Super Contributor
timestamp: March 24, 2016, 09:41:32 pm
content: Additional information. The power supply inside the printer outputs +24V and +3,3V, If you can get to that 24V supply you should be OK. I have a service manual if you need it, send me a PM.Also, pin 35 on the Centronics connector should be at 5V with pin 33 at ground.

author: SeanB
author_rank: Super Contributor
timestamp: March 25, 2016, 07:05:55 am
content: Centronics port typically has a series resistor on the 5V line, around 100R, for protection. Under the printer ( even under the additional paper trays, you can put up to 6 in these printers, so you can either have a feeder that takes an entire box of paper, or have multiple different paper types and sizes, as I found out when installing the service fuser kit, and had a whole load of feed rollers left over, and instructions on putting them in the feeder trays) there is a socket, with a whole load of purple wires connected to it leadin up inside the printer.The socket you will need to pull from another failed printer, as it is a interesting sliding contact design, but you will find a 24VDC rail on it. The paper feeder has a small onboard logic board, which has a 7805 regulator on it to give 5V at 100mA for the onboard microcontroller, and a motor driver and solenoid drive, to lift the paper tray and operate a paper feed solenoid respectively. The 24V supply can supply 1A to all the attached feeders, though typically only one at a time is actually drawing current, either for paper tray raising, or for triggering the gear mechanism passing through the tray to grab a sheet of paper and feed it up the paper path, either direct to the printer or via the upper casettes. You can connect as German EE has said, a small switching regulator ( cheap eBay one will do, it just has to have a 1A rating, which means it should do 500mA safely) will fit on the 24V line and power your WAP device.Just took one of these printers ( a close relative 3500, but the same construction though) apart, and still have the whole wiring loom around with most of the connectors still on, not sure if I kept the accessory paper feed side socket though. Power supply is 2 separate switchers, one switched one doing the 24V rail, and a separate switcher ( on the same long board in the side of the printer) doing the 5V rail, so the 24V supply may disappear when the printer goes into standby, so the AP will switch off if powered from 24V. You probably will have to go into the printer and grab a feed off the 5V rail though, so you can still wake the printer when it goes into power save mode, which it will typically do after 2 minutes.

author: RiverTown
author_rank: Regular Contributor
timestamp: March 25, 2016, 12:09:31 pm
content: Wow, guys thanks for info. I'll try to answer on all posts.Quote from: German_EE on March 24, 2016, 09:09:19 pmHP JetDirect port is used "for easy installation of paper-handling accessories" says manual, but I'll check is there any connectors on the bottom of the paper tray. Thanks SeanB.Quote from: tautech on March 24, 2016, 09:19:21 pmYes, there is Duplex option, and connector is hidden under plastic cover. It is an weird ass 4 pin connector, so I'll have to find male plug. For now I don't know pinout.I'm afraid that linear solution isn't an option, because of high dissipation, I'll use switching converter.Quote from: German_EE on March 24, 2016, 09:41:32 pmYes, I have service manual. 5V for sensors is generated later on..Unfortunately there is no real schematics in service manual, just block diagrams, and wiring schematic.Quote from: SeanB on March 25, 2016, 07:05:55 amFirst of all, thanks Sean for great infos.I'll take a look under the printer today, I haven't done it before because printer is located in limited space environment.Hm, than this connector could be similar to duplexer connector. I will probably make my own switching regulator, so that I don't need to wait ebay delivery. No problems there.I'll try to take and post some pictures of connectors today, so we can identify them.That would be a real bummer if 24V isn't available in sleep mode. I think it is investigation time. At least I hope that there is 5V easily accessible if 24V disappears in sleep mode.Do you maybe have some schematic of 4000 printer? Or more informations about accessory port? Maybe you can take a look yours 3500 series printer, if there is identical port, and how is it wired?

author: SeanB
author_rank: Super Contributor
timestamp: March 25, 2016, 12:26:54 pm
content: 3500 series is currently on it's way to the smelter, and the boards are in the ewaste pile somewhere. The ports are wired in the purple cabling, and go to the mainboard using one of the 10 identical connectors on it. Did not note where the plugs went sorry. Should be easy to find a service manual for the HP printer of yours online, and this should at least show you a block diagram of the wiring, and show which wires go where.

author: RiverTown
author_rank: Regular Contributor
timestamp: March 25, 2016, 02:03:39 pm
content: I've found connector of the bottom of the tray, it is same connector type as the one for duplexer.No problem Sean. I have service manual, but it only showing internal wiring diagram, a wasn't able to find what I'm looking for.Here are some (poor quality) pictures of duplex connector, can anyone recognize which connector type is it? Does somebody have, or know where I can get male part of this connector?

author: German_EE
author_rank: Super Contributor
timestamp: March 25, 2016, 04:20:05 pm
content: Don't you just hate it when they use weird ass connectors, a six pin Molex will do the job just as well but no, they have to be different.

author: SeanB
author_rank: Super Contributor
timestamp: March 25, 2016, 05:03:44 pm
content: It is a HP connector, designed by them to be both easy mating when you drop the printer on the duplexer, self aligning and with wiping contacts that will not vibrate open. There are 3 ground pins and a pair of 24V pins, with a single wire left for the communications. You will have to look for a photo of the duplexer board for more info though, sorry. Or find a similar duplexer ( off another printer) and grab it, then simply use the case to hold the converter and AP as a single unit, with the paper tray glued shut and labelled appropriately.

author: RiverTown
author_rank: Regular Contributor
timestamp: March 27, 2016, 07:56:00 pm
content: I'll try to simulate male connector with pcb, thicknesses are similar. Little solder could help. If that fail, I'll try to find (buy) connector or printer part that has it.