hybridfree/eevblog-posts huggingface dataset:
charging circuit; how to tell if battery is connected? - Page 1
Forum section: electronics / beginners

author: ja421
author_rank: Contributor
timestamp: September 19, 2016, 01:38:23 am
content: I want to build a battery charger. The charging part is not the problem. What I want to do is detect when a battery is connected & disconnected. I cannot simply check for voltage, since voltage would be present during charge.I am totally at a loss as how to determine when a battery is there. Any suggestions on method(s) to use?thank you

author: JS
author_rank: Frequent Contributor
timestamp: September 19, 2016, 02:46:52 am
content: Yo do already sense the voltage and current I guess... When no battery current will be zero and voltage will be non zero, when the battery start to charge current won't be zero, voltage would be lower than the maximum battery voltage, when the battery is fully charged you sill cut the power, so zero current again but you do know you are not charging, if fully charged battery is present you know there is a battery, when it goes down there is no battery. When no battery the supply goes high again, when start sensing current there is a battery again.Complex way to say, the voltage will tell you if there is a battery. When you don't have a battery you don't have voltage or you have too much voltage. You do need to take good care of your max voltage and have stop charging when reached, then all the other are just the conditions you will have during the charger full cycle.JS

author: digsys
author_rank: Unknown
timestamp: September 19, 2016, 02:56:48 am
content: A standard method used in security systems backups etc will work well in this case.Regulations require the battery backup to be tested at least once a day. The usual method is to have a load resistor and FET/BJT switch across the battery.It can be 0.1C or whatever you want. The idea is - stop charging, apply 0.1C load (for 5-15mins) and compare the voltage curve to a preset one.In your case, you'd set say 1/100C load and check for 1-100mS every 5-60 secs. These numbers are just examples.If you don't have a cpu, then you could do it with some simple logic. Make sure you take into account any capacitors and other power sources, IF they are notisolated by a diode OR setup. Maybe you can ideas from this.

author: ja421
author_rank: Contributor
timestamp: September 23, 2016, 07:04:01 pm
content: Thank you both... I have a better handle on it now. I appreciate your help!
Charging conundrum - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 10, 2019, 11:42:16 pm
content: Hi,I'm planning to have a bright LED that runs from battery, I also want a Adafruit Feather M0 WiFi to power from the same battery (unless USB is plugged in) and use the Feather charge circuit to to charge said battery, so I'm pretty sere I need to disconnect the LED when charging, what would be the circuit to do this, a relay, is there anything available off the shelf?Thanks for looking.CheersRichard

author: andy3055
author_rank: Super Contributor
timestamp: October 11, 2019, 01:21:29 am
content: Not sure about all the details of the equipment you are dealing with. Could you use a simple 2-way switch on the +ve lead?

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 11, 2019, 06:10:22 am
content: Thanks, it's one of those Cree LED's on a PCB with a driver PCB from AliExpress.When charging I would want to disconnect the LED automatically.From here:https://learn.adafruit.com/adafruit-feather-m0-wifi-atwinc1500/"We also tied the battery through a divider to an analog pin, so you can measure and monitor the battery voltage to detect when you need a recharge."I wonder if that helps?

author: JackJones
author_rank: Regular Contributor
timestamp: October 11, 2019, 07:23:19 am
content: You don't have to disconnect the LED while charging. You could make a load sharing circuit, they are quite simple. Here's an example:

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 11, 2019, 08:56:08 am
content: Thanks, the Feather board has a MCP73831/2 onboard, does that make a difference?The battery is primarily to run the LED lamp but it should also run the Feather when there is no USB connected, when USB is connected the feather should charge the battery, come to think of it having the lamp run while charging will completely negate the charge current, the lamp is 1W.
Charging current for 3.7V, 300mah lipo battery - Page 1
Forum section: electronics / beginners

author: Toby_CM
author_rank: Newbie
timestamp: February 21, 2022, 01:23:24 pm
content: I have a 3.7V, 300mAH lipo battery. I plan to charge it with TP4056 charging module. But the resistor is 1.2 kΩ which is 1A charging. For safe lipo charging is 1C (300mA in my case). So, I am wondering if I use a power source of 5V, 300mA for TP4056, will be it charging? Since the power source is 300mAH, the battery current draw will only be maximum at 300mAH. Am I right?

author: wraper
author_rank: Unknown
timestamp: February 21, 2022, 01:29:08 pm
content: No, power source will either output more current than it's rated for, or the whole thing will malfunction. You need to replace the resistor for appropriate charging current.

author: Zero999
author_rank: Super Contributor
timestamp: February 21, 2022, 01:48:55 pm
content: This will end in magic smoke and fire.If the power supply isn't current limited, it will be damaged.If the power supply goes into current limiting it will become unstable and the battery still might overcharge.Change PPROGfor 12k, to reduce the current to 100mA.Refer to page 2 of the datasheet.https://dlnmh9ip6v2uc.cloudfront.net/datasheets/Prototyping/TP4056.pdf

author: Toby_CM
author_rank: Newbie
timestamp: February 21, 2022, 02:57:44 pm
content: So even I manage to find a 5v, 300mAH adaptor, it will cause unstable current which will damage the battery?

author: Zero999
author_rank: Super Contributor
timestamp: February 21, 2022, 03:50:45 pm
content: Quote from: Toby_CM on February 21, 2022, 02:57:44 pmThere's no such thing as a 300mAH adaptor. mAh, means milliamps per hour and is a unit of charge, not current.Current refers to the number of electrons flowing per second.Charge corresponds to the total number of electrons transferred, irrespective of the length of time.Charge is analogous to the amount of water in a tank and current the amount of water flowing through a pipe, at a given instant.A charge of 300mAh is: 100mA flowing for 3 hours, 150mA for 2 hours, 300mA for an hour, 600mA for half an hour etc.What you have is a 5V power supply, rated to a maximum current of 300mA. This means no more than 300mA can be drawn from it, before there's a risk of it either overheating, or the output voltage dropping below. mA means milliamps, which is a unit of current, not charge.The TP4056 module is a battery charger. It will deliver a fixed output current of 1A, into a battery, until the voltage reaches 4.2V, then it stops. As mentioned above, the current can be reduced to 100mA by changing PPROGto 12k.
Charging for fabrication - Page 1
Forum section: electronics / beginners

author: tron9000
author_rank: Frequent Contributor
timestamp: September 06, 2017, 09:08:08 am
content: Now then,I've started making my own PCB's at home using toner Transfer method and Ferric Cholride etch and have had a request from a work college about getting a PCB fabricated for their home project.They're willing to pay but I don't know what to charge. Does anybody else do this from home and what rates do you offer? price per mm2? cost of consumables (etchant)?

author: Ammar
author_rank: Regular Contributor
timestamp: September 06, 2017, 09:24:37 am
content: I have etched my own boards and sent boards out for fabrication. I would recommend they send their design out to OSH Parkhttps://oshpark.com/

author: BradC
author_rank: Super Contributor
timestamp: September 06, 2017, 09:54:09 am
content: Yeah, don't do that. I'm the same. Toner at home and fab for anyone else. I'll help layout and design but I don't fab for other people. Too much risk and hassle.

author: tron9000
author_rank: Frequent Contributor
timestamp: September 06, 2017, 10:55:59 am
content: fair enough. Ta Very much.

author: Ian.M
author_rank: Super Contributor
timestamp: September 06, 2017, 11:12:55 am
content: Assuming your workspace is appropriate and you have adequate safety and first aid equipment, showing them how to etch a PCB in exchange for beer and materials is one thing but if cash or other financial remuneration is proposed, or they don't want to participate hands-on, just say NO.

author: tron9000
author_rank: Frequent Contributor
timestamp: September 06, 2017, 12:33:32 pm
content: oddly enough the project is beer related! home brew monitor.I think I need to stress that this is not a business venture. I think the notion of beer in exchange is probably a good idea, less formal and can be easily rectified (buy beer in return)I will ask if they want to watch over, I have safety googles and gloves, first aid, eye wash station, make sure they wear some clothes they don't mind getting spoilt.thanks
Charging liIon batteries - Page 1
Forum section: electronics / beginners

author: Beamin
author_rank: Super Contributor
timestamp: January 04, 2021, 01:40:47 am
content: When charging liIon batteries does each charging chip need to be specific to the mAh of the cell? Or does the chip have a pin where you connect a resistor/cap to specify the mAh? Or does it not matter and the chip detects or doesn;t matter?I would like to convert some older nicd/nimh devices to liion. Surprised china hasnt made dangerous AA/AAA form factor liion's. They already make hot water baby cookers ,electrocution shower heads and radioactive blankets bracelets dildo's.

author: ledtester
author_rank: Super Contributor
timestamp: January 04, 2021, 02:44:51 am
content: Typical Li-ion charging chips have a programmable charge current (not capacity) which you set via a resistor.E.g. google for "TP4056 datasheet".

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 04, 2021, 02:46:10 am
content: You have to set the charging current to be within the limit for the cell, consider the limit 1C if you don't know and ideally 0.5C or lower. Particularly large cells (more than 20Ah or so) are likely to be lower due to less surface area per volume for heat dissipation. As for the charging stop voltage, 4.2V/cell is the most common but if you can find a charger that stops at 4.1V/cell, you'll dramatically increase the service life of the pack.Quote from: Beamin on January 04, 2021, 01:40:47 amI think the "AAs" are better known as 14500s or something like that.

author: Beamin
author_rank: Super Contributor
timestamp: January 04, 2021, 06:40:56 am
content: Quote from: NiHaoMike on January 04, 2021, 02:46:10 amThey do have AA liions?DOHI just found a really old eevblog video on liion batteries. Dont know how I missed it out of the 1000+ videos.

author: BravoV
author_rank: Super Contributor
timestamp: January 04, 2021, 07:40:16 am
content: Quote from: Beamin on January 04, 2021, 01:40:47 amBelow are my 14500 Li-ion cells compared to NiMh, red ones made by Japanese Sanyo/Panasonic UR14500P 840mAh.Not sure why China gets into these narrative.Does this change your attitude against Japanese ? ... just plain stupidity ...
Charging Lithium Ion Polymer Battery with 18650 Charging Board module - Page 1
Forum section: electronics / beginners

author: SmurfKiller
author_rank: Contributor
timestamp: April 04, 2017, 05:36:30 pm
content: Hey Everyone, I have a extra18650 Lithium Battery Charging Board moduleleft over from another project, I was wondering if i could use it to charge something like thisLithium Ion Polymer BatteryMy logic is, they are both lithium batteries right? or am i going to burn down my house? lol.

author: senso
author_rank: Frequent Contributor
timestamp: April 04, 2017, 05:44:46 pm
content: Yes, it will work, but you need to change a resistor to lower the charge current.
Charging phone with low amps - Page 1
Forum section: electronics / beginners

author: Charkel
author_rank: Contributor
timestamp: November 30, 2016, 04:53:41 pm
content: Hello!I know that charging the phone battery with higher amps will shorten the life spawn of the battery.But what about charging with less? With a powerbank or computer for example.Will that have any effect on the battery?

author: suicidaleggroll
author_rank: Super Contributor
timestamp: November 30, 2016, 05:00:33 pm
content: The slower you charge it, the less it damages the battery. Ideally your charge current would be <0.5C, which means it should take at least 2 hours to go from 0% to ~90% charge. A typical 500mA USB 2.0 port on a computer is often a convenient way to accomplish this.Unless you NEED your phone to charge up as fast as possible because you're in a hurry, those crazy high power high speed charging solutions should be avoided.
Charging series Li-Ions with a single cell USB charger. - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: September 21, 2014, 07:06:38 pm
content: I'm wanting to build a device that is powered by 3 x series Li-Ion batteries. The problem is that the only source of charging power I have available is 5V from a usb plug. This is non-negotiable, I can't go into the reasons why, it'd take too long, it's just the way it is, no other port or source of power can be used. The first thing I thought about was to get a balance charging board and charge pump the USB 5V to 12.6V, but this proved next to impossible, costly and quite large PCBs etc.. mot to mention the strain on the USB power, just impractical. So I thought matye I could use a single charger board, you can pick these up on ebay for pennies, they are a single tiny charging board, USB power in and battery terminals out for Li-Ion/Polymer cells. Something like thishttp://www.ebay.co.uk/itm/Lithium-Battery-Charging-Module-Charger-Board-mini-5v-USB-li-ion-charger-tp4056-/390566538252Then somehow switch the battery out points on the charger between the 3 cells, using a small mcu to switch the fets between the cells in rotation, say charge 1 cell for a minute then switch to the next one etc.. This shouldn't allow the batts to get out of balance. Is this a viable option?EDIT: Lol, actually no, forget it. I just realized that the diodes in the fets would muck the whole thing up. Maybe I could use SSRs instead?

author: Simon
author_rank: Unknown
timestamp: September 21, 2014, 07:16:35 pm
content: You still don't escape the fact that you have the same amount of power from one usb port. what about a step-up converter from 5V to your 12.6, you could use more than one USB port in parallel

author: Unknown
author_rank: Unknown
timestamp: September 21, 2014, 07:19:35 pm
content: A charger board only requires 5V if the output of the charger board is switched between the cells it never needs more than 5V because it is only ever charging one cell at a time. I have tried this manually and it works, my problem is automating the switching. Stepping 5 to 12.6 is also no easy task even at 500mA

author: IanB
author_rank: Super Contributor
timestamp: September 21, 2014, 07:25:16 pm
content: If you can find a way to switch the cell connections safely you could charge the three cells together while connected in parallel. If you connect and charge them in parallel they will self balance and the charger will just see one cell of three times the capacity. This would mean of course that you can't have the cells charging while they are in use. The device would have to go offline for charging.

author: Unknown
author_rank: Unknown
timestamp: September 21, 2014, 07:28:29 pm
content: Right, I get what you mean Ian. That's a better option actually. I could use a big 4 pole 2 position switch to do that and cut the power to the main PCB as well. Thanks, Good idea...EDIT: The device could still work, it only needs 3.3V for its display and MCU. Its main function wouldn't work because that requires 8V+ but I could still leave the display on saying "Charging" etc..
Charging ubl aaa batteries - Page 1
Forum section: electronics / beginners

author: fixit7
author_rank: Regular Contributor
timestamp: June 13, 2019, 04:47:36 pm
content: The aaa alkaline batteries went out on my tv remote.I decided to use my NiMh ubl aaa batteries. 1100 mAh.They are currently showing 1.31 volts.And they work ok in the remote as is.My charger is the manual type.It charges those type at 150 mA.I want them fully charged since they are 1.2 volts versus 1.50 for the alkaline.I would like to know how much longer to charge them.Thanks.

author: Audioguru
author_rank: Super Contributor
timestamp: June 13, 2019, 04:58:32 pm
content: Alkaline batteries are not rechargeable. If you try charging them then they might explode or leak.

author: mariush
author_rank: Super Contributor
timestamp: June 13, 2019, 05:19:27 pm
content: Alkaline batteries that are NOT rechargeable have a higher voltage than rechargeable batteries.At their peak, fully charged state, they're close to 1.65v but they'll quickly discharge to around 1.5v and then gradually discharge and give most of the energy until you get near 1v.Rechargeable batteries are different, their nominal voltage is 1.2v and when they're fully charged they're close to 1.35v - it's quite possible your charger simply stops charging them at 1.31v (a bit below 1.35v as safety)Just like the regular alkaline batteries, rechargeable batteries will give most of their energy down to around 1v.

author: fixit7
author_rank: Regular Contributor
timestamp: June 13, 2019, 05:37:04 pm
content: Quote from: mariush on June 13, 2019, 05:19:27 pmI changed post and added nimh.
Charging voltage -  - Page 1
Forum section: electronics / beginners

author: SmurfKiller
author_rank: Contributor
timestamp: February 18, 2020, 12:41:41 am
content: Hi all, I am trying to recycle some e-waste i had lying around the house, and thought i would re-purpose an old laptop battery into a little 12v power pack.I picked up this little 3S 20A 18650 BMS from eBay; i have been trying to find a power supply to charge it, it lists the charging voltage as 12.6 - 13v. now i have an old Samsung 14v power supply that i wanted to use, do you think it would be OK?
Charging with a BMS - Page 1
Forum section: electronics / beginners

author: Dhanushka
author_rank: Regular Contributor
timestamp: August 19, 2019, 09:18:11 am
content: Dear all,I made a battery pack with two 18650 batteries and 2S BMS. Can I charge this pack directly with the BMS without a charging controller safely for user, batteries and other electronics?The BMS is this onehttps://www.aliexpress.com/item/32956998731.html?spm=a2g0o.productlist.0.0.65f9459bADS4De&algo_pvid=62cbec1a-9e48-420a-8c7a-9f7023a10878&algo_expid=62cbec1a-9e48-420a-8c7a-9f7023a10878-1&btsid=acec6a41-6f12-4645-8765-fb4fa9af4a98&ws_ab_test=searchweb0_0,searchweb201602_5,searchweb201603_55Thanks

author: Daixiwen
author_rank: Frequent Contributor
timestamp: August 20, 2019, 07:28:26 am
content: No. The BMS is just a protection circuit. You still need a charger circuit that will control the charge current and limit the charge voltage.

author: kjr18
author_rank: Regular Contributor
timestamp: August 20, 2019, 09:22:40 am
content: You also need to charge it with charger that supports balance charging, or use cells that are very closely matched. This BMS only monitors overvoltage, undervoltage on both cells. And those can drift in charge with many charge/discharge cycles.You could try to use balancer circuits, they are on Ali as well, but I don't know how good are these.
Charging  - Page 1
Forum section: electronics / beginners

author: Ben sage
author_rank: Contributor
timestamp: November 29, 2019, 10:50:41 pm
content: Hi guys I was wondering how this old car battery charger works because it charges battery’s with AC and also at the 12 V setting I measure 50 V I’ve tested it it does work

author: Jeroen3
author_rank: Super Contributor
timestamp: November 29, 2019, 11:01:33 pm
content: As long as there is DC offset it is fine.If there isn’t, the battery lifetime will be halved. (~2 years max)But I suspect you‘re not probing right.

author: Ben sage
author_rank: Contributor
timestamp: November 29, 2019, 11:20:03 pm
content: It’s not DC offset there is negative and positive and I put the ground clip to the negative and the probe to positive

author: xrunner
author_rank: Super Contributor
timestamp: November 29, 2019, 11:22:28 pm
content: Quote from: Ben sage on November 29, 2019, 11:20:03 pmYou seem to be showing 50Vpp on the scope?50 Vpp would be 25 Vpeak, and would then be 17.1 Vrms. I think the charger uses the 50Vpp into a full wave bridge, and then maybe a capacitor, so I don't think it's unreasonable. But as was said,whereare you probing the 50 Vpp is the question.

author: Ben sage
author_rank: Contributor
timestamp: November 29, 2019, 11:43:27 pm
content: Here’s how I hook them up And this is what It looks like inside

author: sleemanj
author_rank: Super Contributor
timestamp: November 30, 2019, 12:01:47 am
content: The plate on the left of your picture looks like a single plate selenium rectifier (what we would now use a diode for), it may well not be doing much in the way of rectification any more.You may find this of use:http://anoldtechniciansworkbench.blogspot.com/2013/01/one-amp-battery-charger.html

author: jmelson
author_rank: Super Contributor
timestamp: November 30, 2019, 02:29:22 am
content: Quote from: sleemanj on November 30, 2019, 12:01:47 amit may also be working fine, just too leaky to show up any DC on a 1 Meg Ohm scope input. Try putting a load like a 20 Ohm resistor (value not at all critical) or a car turn signal bulb on it as a load and try the scope again.Jon

author: james_s
author_rank: Super Contributor
timestamp: November 30, 2019, 06:31:10 am
content: That's exactly what I was going to suggest, put a load on it, IIRC those old selenium rectifiers are pretty leaky.I would probably replace it with a modern diode if I were going to actually use the charger. If the selenium rectifier fails, which they sometimes do, you'll never forget that awful smell.

author: Ben sage
author_rank: Contributor
timestamp: November 30, 2019, 01:43:52 pm
content: I just found out from my dad that we have two of these chargers and this is the broken one So the one I tested does work but not this one and thanks guys for the great comments

author: james_s
author_rank: Super Contributor
timestamp: November 30, 2019, 07:16:20 pm
content: Replace the selenium rectifier with a sufficiently rated diode and that will fix it right up, there's not really anything else to go wrong.
cheap 13.8v power supply for cb/ham? - Page 1
Forum section: electronics / beginners

author: rickselectricalprojects
author_rank: Regular Contributor
timestamp: April 18, 2015, 02:21:43 am
content: hi everybody!i am getting into ham and cb radio and was wondering were i could find or make a cheap 13.8v power supply capable of putting out at least 10 amps. as i am only 14 i dont have a huge budget ($30 max?) and i also dont have a great knowledge of electronics (something not to hard?)thanks!

author: Vgkid
author_rank: Super Contributor
timestamp: April 18, 2015, 02:42:22 am
content: this should work, price is AU 37.50 +4.00eBay auction: #http://www.ebay.com.au/itm/S-120-12a-Super-Stable-Power-supply-unit-120W-DC-12V-10-5-13-8V-10AMP-/111240152688?pt=LH_DefaultDomain_15&hash=item19e66e0670If it will work down to 12v you have more choices. some 12v psu's are adjustable for more voltage.You guys don't get alot of choices, it will be cheaper to buy, unless you can source the rest of the components cheaply.

author: Vgkid
author_rank: Super Contributor
timestamp: April 18, 2015, 03:21:03 am
content: seeing the other thread givves you much more choices.Still at that power level, it is cheaper to buy than build.

author: patw4pbj
author_rank: Newbie
timestamp: April 18, 2015, 03:50:20 am
content: Don't overlook used equipment from other hams in your area. Many long timers may have a spare around and would gladly help out a new/young ham.Sent from my iPad using Tapatalk
cheap 150W 220V soldering pot on 110V? - Page 1
Forum section: electronics / beginners

author: hitachi8
author_rank: Contributor
timestamp: October 06, 2011, 04:52:24 am
content: simple question:can i run a 220VAC soldering pot (150W) on 110VAC?i can change the plug and anything no problem, i just want to know if possible and if so... what will happen?here`s the item link for you curious people:www@dealextreme@com/p/150w-temperature-controlled-soldering-pot-blue-golden-220v-48761i also dont mind modding it, i just want to have one for desoldering tons of component fast and easy withoutpaying 50$.edit: sorry for the stupid question between, but you got the only good electronic forum i know.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 06, 2011, 05:23:03 am
content: I don't think it will get hot enough to work.Also,if the control circuit will even still work,the element will be on all the time.You could get a 110/220 volt transformer,but it will have to be capable of supplying a 150W load (or a bit more,to be sure).My suggestion--too many hassles,keep searching for a 110v oneVK6ZGO

author: metalphreak
author_rank: Frequent Contributor
timestamp: October 06, 2011, 09:08:55 am
content: Half the voltage thus half the current. Running it on 110V means it'll only be heating the element with 37.5WI think the control systems for them are pretty basic but you're better off just finding a 110V model.Look on ebay instead. DX only sell 220V ones.http://www.ebay.com.au/itm/CM360A-Round-Solder-Pot-Soldering-Desoldering-Bath-110V-/390343761863?pt=LH_DefaultDomain_0&hash=item5ae24d1fc7#ht_2089wt_1163

author: hitachi8
author_rank: Contributor
timestamp: October 06, 2011, 02:46:18 pm
content: alright, thank you for your answer.
Cheap alternative to Panavise products?. Exists?. - Page 1
Forum section: electronics / beginners

author: adlfdlf
author_rank: Newbie
timestamp: September 26, 2012, 12:02:40 am
content: I look for a cheaper alternative to Panavise products (Panavise 333, 315 + 380, etc.). Any recommendations of where to search?. Sorry for my poor english.Thanks!.

author: GeoffS
author_rank: Unknown
timestamp: September 26, 2012, 12:06:21 am
content: A quick search revels this thread that might be of help.https://www.eevblog.com/forum/beginners/pcb-board-holder-what-are-you-using/msg105247/?topicseen#msg105247
Cheap ammeter input impedance ?    - Page 1
Forum section: electronics / beginners

author: Back2Volts
author_rank: Unknown
timestamp: November 10, 2016, 03:52:44 pm
content: This cheap ammeter gives a spec of Input impedance: 5m?. Are they talking about the sense current resistor?http://www.ebay.com/itm/35-19-10mm-Mini-Ammeter-Meter-0-5A-Red-LED-0-36-3-Digital-Panel-BE-/201709674896?hash=item2ef6d56190:g:nS8AAOSwZVlXjyfE

author: Kleinstein
author_rank: Super Contributor
timestamp: November 10, 2016, 04:21:47 pm
content: The 5 mOhms is the shunt resistor. You have to add a little for the wires which is something like 17 mOhms per meter for 1.5mm² lines and a little for the board.
Cheap and easy to mount buttons - Page 1
Forum section: electronics / beginners

author: scrat
author_rank: Frequent Contributor
timestamp: March 18, 2011, 04:49:59 pm
content: Hi all,I need to add some buttons to a board, but since it has to be put into a plastic box, I don't know which is the better way. I don't want to use rubber caps or similar, since mounting them doesn't seem to be easy (but if someone says it is, why not?).The only idea I have had is to use tactile pushbuttons that have a long head, which will go through a hole in the box, but I don't know if so mounted buttons will be easy to press and enough robust.Any alternatives?

author: deephaven
author_rank: Frequent Contributor
timestamp: March 18, 2011, 05:07:09 pm
content: I've used MULTIMEC - 3ETL9-15.0 - SWITCH, SPNO, 15MM available from Farnell. They are easy to use because they come with a range of actuator lengths so you just pick the one that matches your mechanical design. The actuators also have a bit of lateral play which takes care of any tolerances in the position of your holes!

author: scrat
author_rank: Frequent Contributor
timestamp: March 18, 2011, 06:04:50 pm
content: Great!Besides I couldn't easily find switches like these on Farnell, where I was searching, (but I would have tried harder), I wanted to have an advice from someone more experienced.Thanks!
Cheap Arduino kit, why do I read forums ? - Page 1
Forum section: electronics / beginners

author: Deathwish
author_rank: Unknown
timestamp: May 12, 2015, 06:04:53 am
content: I have managed to stay clear of such things as the Arduino etc , mainly because of costs for something I might never really use, but last night i found a web site that is as far as I am concerned as cheap as chips.I only went looking because of Daves youtube vid on Arduinos I watched then read a few posts on here, so I splashed out with my income as it is and purchased a few things, now I just need Dave etc to tell me how to turn them into the next mars rover. Seriously a £2 price for mains relays etc and £4 for the arduino itself, I went mental and got the mega too and an lcd etc etc.Dont shoot me for linking it as I am unsure if I am allowed to. but go have a look and see what you think of their prices.http://www.gearbest.com/arduino-_gear/

author: smjcuk
author_rank: Frequent Contributor
timestamp: May 12, 2015, 06:47:48 am
content: Bought a few of those cheap things. Usually pretty good. Got an arduino for £2.25 shipped off aliexpress to use as an AVR programmer - works nicely even if the soldering was a bit wonky and the thing was a lurid yellow. The USB cable was shit that came with it but that was all.Doubt I'd ever hit the 'mainstream' stores now. Putting down 8-20x the cash on the table isn't realistic.

author: chibiace
author_rank: Regular Contributor
timestamp: May 12, 2015, 09:04:17 am
content: once you have one working you can program more atmega chips up with the bootloader andnthats when those ftdi breakouts are handy, have a look at energia too which is an arduino-like ide for some msp430 uC like on the ti launchpad.

author: picandmix
author_rank: Frequent Contributor
timestamp: May 12, 2015, 09:42:57 am
content: You only have to search the web to find many Arduino parts are avaiable from within the UK at very similar prices, typically the same but plus uk postage.Saves waiting weeks for them to arrive, and also weeks if anything is wrong with them.

author: ElectroNub
author_rank: Contributor
timestamp: May 12, 2015, 10:29:04 am
content: Get more than one! Sometimes the cheapo stuff is defective. Or you might let the magic smoke out on accident.I try to test everything on a "sacrificial" $2 pro-mini clone before hooking up to a more expensive board. You can get a 5 pack for around $12.It is too easy to learn that lesson the hard way. I had a stupid temp sensor short 12v into my 'genuine' Mega. Think I paid $50 for the Mega... The whole bag of 10 temp sensors was bad. (beware of LM35)

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 12, 2015, 11:07:34 am
content: Quote from: Deathwish on May 12, 2015, 06:04:53 amso you managed to miss alot of fun.Quote from: Deathwish on May 12, 2015, 06:04:53 amdont count on that.Quote from: Deathwish on May 12, 2015, 06:04:53 amyou are welcome to do so. if anyone want to shoot you, its the PIC fanboys. the link you provided, is... "poka damn sticker" in ebay, if i heard that term right from dave's mouth. as i said, you missed alot of fun already.
Cheap automatic stripper "settings"? - Page 1
Forum section: electronics / beginners

author: kalel
author_rank: Frequent Contributor
timestamp: September 21, 2017, 10:52:20 pm
content: I know there might be a thread, but this question is about this specific model:https://youtu.be/NWLhnqxdM7k?t=390I have one of these as well, and they always seem to cut the insulation as well, so I wonder the same thing as the video author. I don't think there are any settings to make it work, are there?

author: John B
author_rank: Frequent Contributor
timestamp: September 21, 2017, 11:23:44 pm
content: I have the other variety, the ones that pull sideways. Even though mine are pretty good quality and generally are very accurate where they strip, I usually use a blade (box cutter etc) to partially cut through the insulation. Even cheaper strippers should then make a perfect disconnection at the desired point.

author: Brumby
author_rank: Unknown
timestamp: September 22, 2017, 07:28:21 am
content: Quote from: kalel on September 21, 2017, 10:52:20 pmDo you mean they cut theconductorsas well?QuoteYes. That silver thumbscrew.https://youtu.be/_6yq6FaIFAY?t=207

author: kalel
author_rank: Frequent Contributor
timestamp: September 22, 2017, 03:09:10 pm
content: Quote from: Brumby on September 22, 2017, 07:28:21 amSometimes the conductors, but generally I mean the insulation can get damaged a bit where the cable is "held".A crude drawing:The "wire" is visible on the right, but there's some damage represented by the yellow line. It's usually not jagged and the wire seldom looks like that, cables are not usually rectangles either, just a crude drawing.Yes, I understand there are settings on the back, and I tried adjusting the screws but with not much luck. Probably I'm not using the optimal size cables (I'm not sure what those are). I get much better results with manually cutting the insulation with something as lightly as will allow pulling it off with fingers. This method is much slower, and it is possible to cut too much (possible with the automatic strippers as well).

author: Brumby
author_rank: Unknown
timestamp: September 22, 2017, 11:24:11 pm
content: Quote from: kalel on September 22, 2017, 03:09:10 pmUnfortunately, that's something which is not uncommon.Some things that can affect how bad this problem are:- the quality and thickness of the insulation. Thin and/or weak materials are going to crush more easily.- the speed at which you operate the stripper. A slow, deliberate squeeze gives more time for the insulation to deform, but a quick action might yield a better result.- the gripping area of the jaws around the insulation. These "T-Rex" type strippers don't have a large area to grip the insulation, so the force required to hold it in placed creates greater pressure, giving more deformation. Increasing this contact area/reducing the pressure isn't easy as anything you might try - such as sleeving or a piece of tape - may not offer the same grip and the insulation could slip through.I just dug out my old set of these ... and discovered the top jaw has cracked. They wouldn't strip the skin off a custard now....
cheap bench psu for retro work - Page 1
Forum section: electronics / beginners

author: cypher007
author_rank: Contributor
timestamp: April 30, 2020, 12:08:46 am
content: after a reasonable psu for powering general electronics and 8 bit computers when repairing them.would like upto 30v but 15-16v would probably do.maybe something like this?https://uk.farnell.com/tenma/72-10495/power-supply-2ch-30v-5a-adjustable/dp/2251947

author: Mp3
author_rank: Frequent Contributor
timestamp: April 30, 2020, 08:54:37 am
content: You should be good as long as you have at least 1a of 0-24v, if it tops at 15-16v make sure its a good amount of current,

author: Wytnucls
author_rank: Super Contributor
timestamp: April 30, 2020, 09:03:48 am
content: Here is a cheap HP retro one for you: eBay 50 quid or less plus postage

author: mikerj
author_rank: Super Contributor
timestamp: April 30, 2020, 09:16:00 am
content: Quote from: Wytnucls on April 30, 2020, 09:03:48 amThat's a lovely little PSU (quite tempted), but it's a high voltage and low current supply, not really ideal for the OP's requirements. Old 8 bit machines typically draw over 1 Amp at lower voltages.

author: Wytnucls
author_rank: Super Contributor
timestamp: April 30, 2020, 09:26:59 am
content: Yes, I misread the amp scales. Pity. Was keen on it myself!

author: Mp3
author_rank: Frequent Contributor
timestamp: April 30, 2020, 09:27:26 am
content: The biggest issue with old computers is gonna be onrush currect more than actual draw you have to account for

author: cypher007
author_rank: Contributor
timestamp: April 30, 2020, 09:47:57 am
content: what about these:https://www.ebay.co.uk/itm/Lavolta-BPS305-Variable-Linear-Adjustable-Lab-DC-Bench-Power-Supply-0-30V-0-5A/191766020330?_trkparms=aid%3D555021%26algo%3DPL.SIMRVI%26ao%3D1%26asc%3D20190711100440%26meid%3D46749d6d6bbd4cc89e853b2d38ea2531%26pid%3D100752%26rk%3D5%26rkt%3D17%26mehot%3Dpf%26sd%3D184068045547%26itm%3D191766020330%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplRVIAMLv5WebWithPLRVIOnTopCombiner&_trksid=p2047675.c100752.m1982plus not sure i need a dual setup.Wytnucls thanks for the suggestion, im actually looking for a power supply for retro computer work not a retro psu. lol.

author: cypher007
author_rank: Contributor
timestamp: April 30, 2020, 11:09:31 am
content: was looking at these:so maybe not unless theyve fixed this issue?

author: cypher007
author_rank: Contributor
timestamp: April 30, 2020, 04:02:15 pm
content: is it right they have fixed the problem with them going pop?also as im using it on older computers i assume Linear is preferable?lastly do i need a programmable or just adjustable? its getting confusing on Farnells site as they all look very similar.

author: cypher007
author_rank: Contributor
timestamp: April 30, 2020, 07:54:06 pm
content: anyone know?

author: cypher007
author_rank: Contributor
timestamp: May 01, 2020, 11:04:07 am
content: ok bought one of these:https://cpc.farnell.com/tenma/72-2540/power-supply-1ch-30v-5a-prog/dp/IN07294not sure why a $100 psu is £96, but was the cheapest i could find.anyone know if it comes with the huge bunch of adapter ends like the Korad ive seen unboxed on youtube?
Cheap BGAs to practice soldering - Page 1
Forum section: electronics / beginners

author: newbie666
author_rank: Regular Contributor
timestamp: January 21, 2019, 05:00:45 pm
content: Hello,Can you please recommend me some cheap BGAs I could order at mouser / farnell to practice my soldering skills? I will create a PCB containing a couple of those so really no limitations on what they would be.I was thinking BGA-36 to 96 max. I don't think I will ever have a need to solder something bigger.One idea I had was to create a uC breakout board because then it would be easy to verify that all the balls have been soldered correctly by outputting a square wave or something. Needless to say I don't have an xray to check if I did a good job.Thanks!

author: elecman14
author_rank: Unknown
timestamp: January 21, 2019, 05:11:53 pm
content: Not sure if having a working micro controller would verify all the balls are soldered. You could check out these but they do fit in your cheap criteriahttps://www.topline.tv/drawings/pdf/WLP/WLP36T.3C-DC067D.pdfYou could also try to find something that could do jtag boundary scan. That would be cheaper but probably able to verify more of the pins. Also BGA mirrors are helpful for verification without an X-ray.

author: newbie666
author_rank: Regular Contributor
timestamp: January 21, 2019, 05:37:12 pm
content: Topline kits look good, especially this one:http://www.topline.tv/963000_Kit.htmlI can't find any distributors though and minimum order for export is >1000USD

author: TheDane
author_rank: Regular Contributor
timestamp: January 21, 2019, 06:08:53 pm
content: Grap a bunch of cheap SBC's with a BGA the size you'd like to practice on.Lift it - put it back on, and see if it still works

author: james_s
author_rank: Super Contributor
timestamp: January 21, 2019, 06:12:18 pm
content: To do that you have to re-ball the ICs.You could just use the parametric search on Digikey, Mouser, etc and search for BGA packages then sort by price.

author: TheDane
author_rank: Regular Contributor
timestamp: January 22, 2019, 09:33:30 am
content: Reballing - use a stencil, and some solderpaste or use the right sized ball(s).https://www.google.com/search?q=bga+stencil&source=lnms&tbm=isch&sa=XFrom what I know, it is not always BGA's come pre-balled - so it is a great skill to (also) possess if you want to be great at soldering BGA's.
Cheap Bluetooth module to act as HID  - Page 1
Forum section: electronics / beginners

author: sairfan1
author_rank: Frequent Contributor
timestamp: July 04, 2022, 05:30:59 pm
content: I'm looking for a cheap Bluetooth modules to act as HID (human interface device) with Andriod or iOS. I want to only send keys, typing letters to focused input box.Does anyone has experience using HC-06 or some other low price module.

author: matb
author_rank: Regular Contributor
timestamp: July 05, 2022, 12:15:54 pm
content: I tried following the HC-05 HID compatibility tutorials, never managed to make it work.Then I went with Adafruit BLE modulehttps://www.adafruit.com/product/2633SPI or UART but they are not cheap 17$.Now I use ESP32 it works and it is designed to, no modification of firmware and whatever just working. I used this libhttps://github.com/T-vK/ESP32-BLE-Keyboardworks very well. (I had to use press and release the write function didn't work quite well) For 5-7$ maybe cheaper on Chinese market

author: PatrickCPE
author_rank: Newbie
timestamp: July 05, 2022, 12:28:48 pm
content: There are some Bluetooth enabled boards from Arduino if you want to hit the ground running. Fairly cheap little pieces of kit and they're nice if you want something easy to just make a system work. Make sure the bluetooth mode supported is the one you need for your project.https://store-usa.arduino.cc/products/arduino-nano-33-iot
Cheap buck switcher/controller capable of 100% duty cycle ? - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: August 23, 2012, 10:10:29 am
content: Sort of like the common jelly bean MC34063 switcher, but capable of fully 100% duty cycle, does it exist ?I'm aware there are many choices from different IC makers like Linear, TI and etc, its just most of them are exotic and not that easy to source like the MC34063 or those common National Simple Switcher family ics.It doesn't need to be highly efficient, heck, even 70% is more than enough and switching freq at < 500Khz is fine too, and if it has thru hole version, that is even better.Targeted circuit is just a simple adjustable step down from 12 volt source to drive a DC motor (a drill) ranging from 5 volt up to full 12 volt as the source, with 2 or 3 Amp max.Since its driving a motor, output voltage ripple and the regulation performance like transient response are not that critical.

author: BravoV
author_rank: Super Contributor
timestamp: September 08, 2012, 04:56:51 pm
content: Bump ?

author: AndyC_772
author_rank: Super Contributor
timestamp: September 08, 2012, 05:59:48 pm
content: I doubt there are any such devices, not least because although 100% is easy enough, duty cycles very close to 100% are impossible because of the finite amount of time it takes to turn a transistor on or off. Since most power supply control ICs are built around analogue control loops, they'll always max out at some point below (say) 90% duty cycle.It doesn't sound like you actually need a regulated supply like that, though. Can you not build a circuit to generate a rectangular wave with variable duty cycle, and use that to turn the 12V supply to the motor on and off?I built a circuit to control power to an electric heater last year, which doesn't sound like too dissimilar a problem. It consists of a relaxation oscillator and a comparator; the oscillator provides a voltage that goes up and down, and the comparator generates an output which indicates whether the oscillator voltage is above or below some variable threshold. Set the threshold outside the oscillator's range and you get 100% output duty cycle. Gradually lower the threshold voltage and you can get a continuously variable duty cycle all the way down to 0.
Cheap, but ok solderpaste for german hobbyist? - Page 1
Forum section: electronics / beginners

author: Leonelf
author_rank: Contributor
timestamp: April 30, 2015, 03:43:17 pm
content: Hi!I want to get into hot air smd soldering since I find it quite annoying to solder each individual cap with a chisel tip (tssop etc work great, but i hate the little stuff).First Question: Is solderpaste even required for hotair soldering, or can I just pretin the pads?Second Question: Which solderpaste should I use? It doesn't have to be the "greatest" stuff, should just work. I live in Germany (for source of it).Third Question: How much solderpaste would I even need (in gramms)?Thanks for reading!
Cheap china serial hub - Page 1
Forum section: electronics / beginners

author: con-f-use
author_rank: Unknown
timestamp: February 21, 2018, 10:42:28 am
content: I'm getting annoyed by multiple usb-to-serial cabels on my desk.Do you know of a cheap 4-port, or preferably 8-port, serial hub that connects to a computer via USB? Basically something like in the picture below, just for TTL:I would actually prefer just a board without casing. Also, 0.1" pin-headers instead of the d-sub connector seem like a good idea.Otherwise it's an 8port-USB hub and 8 of these:But that's a bit messy, too.

author: Vic20
author_rank: Contributor
timestamp: February 21, 2018, 11:51:56 am
content: I suppose you know that, but the two solutions you propose are not always equivalent.A box with D connectors will probably use standard RS-232 signaling voltages.A device like the small one you show on the photo will probably use TTL signaling voltages.Just check the specs to be sure.

author: con-f-use
author_rank: Unknown
timestamp: February 21, 2018, 12:29:14 pm
content: Yes good point, thanks. I'm aware that the relevant EIA RS-232-C specification mandates -15 < V- < -3V and 3V < V+ < 15V.I have not seen anything produced in the last 5 years that actually had much more then 5V swing, though.To be clear, I'll be using the thing for modern electronics, not legacy devices. That means I'm fine with either 3.3V or 5V TTL signal levels,not finewith anything above 6V and negative voltages with respect to common ground.

author: newbrain
author_rank: Super Contributor
timestamp: February 21, 2018, 02:30:28 pm
content: Quote from: con-f-use on February 21, 2018, 12:29:14 pmIn that case, consider that:The negative swing is (generally speaking) not acceptableThe logic levels are inverted with respect to a "TTL" interface, see picture courtesy of Wikipedia
Cheap chinese 220v->5v transformator board safe? - Page 1
Forum section: electronics / beginners

author: prebs
author_rank: Newbie
timestamp: August 21, 2014, 07:37:12 pm
content: i found this in my parts bin, and I think it's from some cheap chinese electronics from ebay. I would like to re-purpose this for another project, but I don't know much about power supplies.Given that this is from china I'm worried that i might not be too safe, especially given the few components.It's rated for 300-500mA out, 120-220 AC in. I only need 100mA at 5v DC so that should be okey.https://www.dropbox.com/s/jkijcwfgabvbi5p/bilde%201.JPGhttps://www.dropbox.com/s/4ppyqstdq68el6m/bilde%202.JPGWould you trust it ?

author: SeanB
author_rank: Super Contributor
timestamp: August 21, 2014, 07:55:19 pm
content: Safer than a lot I have seen. Decent isolation slots between the mains and LV side, but no RF suppression capacitor ( though the board is marked for one but it is not installed, top of the first pic), and the input actually uses a fusible resistor and a real bridge rectifier.Might not pass insulation test on the transformer, but likely will work well enough as a simple poorly regulated supply, as there is no secondary side feedback so the output voltage is going to vary with load somewhat, depending on the primary side regulation to keep it reasonably constant. You might find that at no load it might deliver closer to 6V than 5V, though likely at 500mA it likely will only deliver 4V5.

author: prebs
author_rank: Newbie
timestamp: August 21, 2014, 08:03:30 pm
content: Cool, thanks for the feedback. That made me feel much safer