author
4Instructables407,263Views174CommentsPittsburgh, PA, USAJoined April 29th, 2010
I have a Masters degree in Electrical Engineering from Carnegie Mellon and have been working in the field of Automation, Robotics and Embedded Systems for over 20 years. I've always enjoyed tinkering/inventing/making things with my hands and love the Maker community, with all the openness and creativity it brings.

Tell us about yourself!

Complete Your Profile

Achievements

100+ Comments Earned a bronze medal
10K+ Views Earned a bronze medal
  • richfiddler11 commented on richfiddler11's instructable Altoids Tin 1/8" Stereo Mixer4 days ago
    Altoids Tin 1/8" Stereo Mixer

    ...note that some audio devices have protective circuitry that switches off the output when they see too little impedance...The solution is to add a resistor in front of the output jack ground, of course at the expense of volume drop. Hi Ralf, I couldn't agree with you more about avoiding too low an impedance load on the audio outputs/mixer inputs (lower impedance = higher power). However, I'm puzzled by your comment since the circuit here does exactly what you're suggesting:   it puts an impedance in line with each input so that the loading on them will be minimal (and it does come at the cost of reduced volume). Most headphone outputs are OK with loads as low as 8-16 ohms.. when plugged into the mixer here, they see nearly 100x that impedance (meaning on t...

    see more »

    ...note that some audio devices have protective circuitry that switches off the output when they see too little impedance...The solution is to add a resistor in front of the output jack ground, of course at the expense of volume drop. Hi Ralf, I couldn't agree with you more about avoiding too low an impedance load on the audio outputs/mixer inputs (lower impedance = higher power). However, I'm puzzled by your comment since the circuit here does exactly what you're suggesting:   it puts an impedance in line with each input so that the loading on them will be minimal (and it does come at the cost of reduced volume). Most headphone outputs are OK with loads as low as 8-16 ohms.. when plugged into the mixer here, they see nearly 100x that impedance (meaning on the order of 1/100th the power required). Perhaps you should take a closer look at the schematic. In all the years this project has been up, most folks have questioned the need for the resistors, but you're the first person to ever say that it doesn't go far enough in protecting the outputs of the devices plugged into it!! Cheers, Rich

    Hi Ralf,re: a line output needing higher impedance, yep OK, I get what you're saying... hmm.. you might be better off with an active buffer of some kind.. unity gain op-amp follower or something like that. I'm afraid that the signal reduction due to higher impedance and the need to boost the gain later on will aggravate the ground noise problem you're having otherwise. The isolation transformer might help, but an active boost on your projector output might be the way to go. If you can find an old NTSC video distribution amp/splitter, those have an audio buffer and people pretty much throw them away these days because of HDMI... just a thought.. good luck!Rich

    View Instructable »
  • richfiddler11 followed Mikhandmaker.1 month ago
      • Wooden Spokeshave
      • Sanding Saw
      • Router Plane
  • richfiddler11 commented on Mikhandmaker.'s instructable Wooden Spokeshave1 month ago
    Wooden Spokeshave

    As someone who clearly appreciates hand woodworking, you'd enjoy using a scraper plane (or even just a hand scraper ). Have a look at the no. 80 Stanley Scraper plane and you'll see why I thought of it looking at your spokeshave.. here's a good article.. https://www.popularwoodworking.com/woodworking-blogs/chris-schwarz-blog/cheap-thrills-the-no-80-cabinet-scrapercheers and thanks for the nice insructable.. -Rich

    View Instructable »
  • richfiddler11 commented on Mikhandmaker.'s instructable Wooden Spokeshave1 month ago
    Wooden Spokeshave

    Beautiful workmanship on the piece and very nice Instructable. I like the beech and brass look. I think you need a matching handmade scraper plane!

    View Instructable »
  • richfiddler11 followed MichielD99 and mikeasaurus3 months ago
      • Make Your Own High Quality CO2 Lasercutter! With Touch Control!
      • Make a Z-axis for Your Laser Engraver!
      • Arduino Laser Engraver Wood Design!
      • Table Saw Class
      • Easy Table Saw Sled
      • 5 Ways to Remove a Stripped Screw
  • richfiddler11 commented on mikeasaurus's instructable Best Ginger Beer3 months ago
    Best Ginger Beer

    wow, I suddenly have a craving for a spicy ginger beer... will have to give this a try!

    View Instructable »
  • richfiddler11 commented on mikeasaurus's instructable Saw Handle Push Stick3 months ago
    Saw Handle Push Stick

    ha ha, yeah I hear you on that... my family has a strong packrat streak too. BTW, I found a tutorial on sharpening a handsaw http://workshopcompanion.com/KnowHow/Tools/Sharpening/8_Sharpening_Hand_Saws/8_Sharpening_Hand_Saws.htmmight be worth a try. I've refurbished old hand planes and they're a joy to use.

    View Instructable »
  • richfiddler11 commented on mikeasaurus's instructable Saw Handle Push Stick3 months ago
    Saw Handle Push Stick

    nicely done instructable but I can't help but feel bad about destroying an old tool like that. I've restored some old tools with great results and have no idea how you'd sharpen a big handsaw saw like that, but I guarantee if it lasted this long, the steel and wood are much better than what you can buy today. It looks nice though and I'd do it if the saw handle didn't have to be modified... maybe join the handle to the shoe with a steel plate or similar.

    View Instructable »
  • richfiddler11 followed UtkarshVerma5 months ago
      • Universal Mini OMTP ↔ CTIA Adapter - Convertendo
      • Handheld PCB Drill
      • ATmega8 As Arduino (using Internal 8Mhz Crystal)
  • Universal Chat Mic -- DIY Gaming/Comm Headset

    Utkarsh Verma -- No!! Please don't remove it! There are often many ways to solve a problem and I don't think having a switch there is foolish at all. It was clever of you to think of it on your own and you did a very nice write up. It may not be the absolute simplest solution, but that doesn't mean that it's not a valid and useful solution, and it may have some advantages. So look at the tradeoffs of the 2 different solutions:- With your switch solution, the user commits (more or less) to having your adapter plugged into the phone all the time. The advantage is that whatever headset they choose to plug into their phone can be made to work. - With the simple cross-wiring adapter I mentioned, the advantage is that if the phone and headset match, you don't need an adapter at all (same appl...

    see more »

    Utkarsh Verma -- No!! Please don't remove it! There are often many ways to solve a problem and I don't think having a switch there is foolish at all. It was clever of you to think of it on your own and you did a very nice write up. It may not be the absolute simplest solution, but that doesn't mean that it's not a valid and useful solution, and it may have some advantages. So look at the tradeoffs of the 2 different solutions:- With your switch solution, the user commits (more or less) to having your adapter plugged into the phone all the time. The advantage is that whatever headset they choose to plug into their phone can be made to work. - With the simple cross-wiring adapter I mentioned, the advantage is that if the phone and headset match, you don't need an adapter at all (same applies for your switch too). The *disadvantage* is that when you need the adapter, you might not be able to find it.I didn't mean to discourage (sorry if I did) but I did want to make sure you understood my point. I hope you keep coming up with ideas and writing instructables. If you ever want to bounce ideas off someone, I'd be glad to discuss more with you (I am an electrical engineer).Take care,Rich

    View Instructable »
  • Universal Chat Mic -- DIY Gaming/Comm Headset

    I do understand your switch adapter 100%: In one switch position It's passing all 4 connections straight through and in the other position it's swapping the sleeve and ring2. It's up to the user to figure out which switch position works for their particular headset/phone combination. This is very simple to understand.I'm simply pointing out that you can get the *exact* same functionality with a simple CTIA-OMTP adapter (crossed sleeve and R2). It's up to the user to decide if the adapter is required or not. This is in fact what I've been doing for years now.Here's a commercial CTIA-OMTP adapter on Amazon https://www.amazon.com/dp/B01I507X4W/

    View Instructable »
  • Universal Chat Mic -- DIY Gaming/Comm Headset

    Hey UtkarshVerma: No need to autodetect, add circuitry or a switch. To solve the problem of adapting a headset of one type (OMTP/CTIA) to a phone of a different type (OMTP/CTIA) you only need a simple adapter that swaps the Sleeve and R2 (Tip and R1 are passed straight thru). There are really only 2 cases: * Case 1: headset and phone use same standard (OMTP or CTIA). Solution: No adapter needed, plug headset straight into phone.* Case 2: headset and phone don't match. 2 possible sub-cases (omtp->ctia and ctia->omtp) but both are solved with the same adapter.Solution: Swapping Sleeve and R2 works for both. Wiring chart in the pic below. Map it out with OMTP on the input, CTIA on the output and vice versa and you'll see it works for both (unless I've *really* missed something).BTW, ...

    see more »

    Hey UtkarshVerma: No need to autodetect, add circuitry or a switch. To solve the problem of adapting a headset of one type (OMTP/CTIA) to a phone of a different type (OMTP/CTIA) you only need a simple adapter that swaps the Sleeve and R2 (Tip and R1 are passed straight thru). There are really only 2 cases: * Case 1: headset and phone use same standard (OMTP or CTIA). Solution: No adapter needed, plug headset straight into phone.* Case 2: headset and phone don't match. 2 possible sub-cases (omtp->ctia and ctia->omtp) but both are solved with the same adapter.Solution: Swapping Sleeve and R2 works for both. Wiring chart in the pic below. Map it out with OMTP on the input, CTIA on the output and vice versa and you'll see it works for both (unless I've *really* missed something).BTW, I don't have any problem with arguing (discussing, debating, whatever you want to call it) as long as it's fact-based and not personal. If someone can show me a better way to do something, a different point of view or a flaw in my reasoning, I'm open to that.

    View Instructable »
  • Universal Chat Mic -- DIY Gaming/Comm Headset

    Yeah, no problem. It is relevant and might help somebody. Nicely done instructable, BTW! One point on your adapter: couldn't you get the same effect without the switch? i.e. if the headset and device are of the same type (OMTP or CTIA) you don't need an adapter. OTOH, If they're not compatible, wouldn't a fixed adapter that swapped the sleeve and the ring closest to the sleeve handle both cases? Just seems like that would be easier.

    View Instructable »
  • Universal Chat Mic -- DIY Gaming/Comm Headset

    I do cover OMTP vs CTIA in the instructable already. Seems like you're really just promoting your own instructable here, but at least it is relevant and if somebody doesn't want to buy a commercial adapter then at least your project is a good alternative. Good luck with that.

    View Instructable »
  • richfiddler11 commented on richfiddler11's instructable Altoids Tin 1/8" Stereo Mixer7 months ago
    Altoids Tin 1/8" Stereo Mixer

    Hi Ferkijel, you're fine. The outer sleeve on the RCA is common (ground) as is the case, so having them touch is not a problem at all. Post a picture when you're done! Rich

    View Instructable »
  • richfiddler11 commented on richfiddler11's instructable Altoids Tin 1/8" Stereo Mixer7 months ago
    Altoids Tin 1/8" Stereo Mixer

    Hey, nice work and glad you liked it! Thanks for sharing the pictures. I love the "Tin-tin tin" but it seems like you should make some kind of divider so you can store cables or something in the extra space! Nice job! -- Rich

    View Instructable »
  • richfiddler11 made the instructable Couch KBM (keyboard/mouse on the Couch)7 months ago
    Couch KBM (keyboard/mouse on the Couch)

    Hey, I'm sorry I missed your comment for so long! (busy lately) Not sure if you built anything or not yet, but I use a double keyboard setup every day (attached some pictures). It looks pretty funky, and is a bit heavy, but it definitely does the job! A few comments:- This is 3rd or 4th iteration, it keeps evolving over time. - two pieces of thin, light board separated by a 3.25" riser - masonite pegboard is nice because you can easily use cable ties to capture wires, etc, but the 1/4" luan plywood is lighter- wide enough to span the outside width of my recliner- there's a small USB hub hidden between the layers. - lower keyboard/mouse attached to hub - a 10-ft heavy-duty USB extension cord that acts as a detachable tether. (this and another wire with power for a USB LED ...

    see more »

    Hey, I'm sorry I missed your comment for so long! (busy lately) Not sure if you built anything or not yet, but I use a double keyboard setup every day (attached some pictures). It looks pretty funky, and is a bit heavy, but it definitely does the job! A few comments:- This is 3rd or 4th iteration, it keeps evolving over time. - two pieces of thin, light board separated by a 3.25" riser - masonite pegboard is nice because you can easily use cable ties to capture wires, etc, but the 1/4" luan plywood is lighter- wide enough to span the outside width of my recliner- there's a small USB hub hidden between the layers. - lower keyboard/mouse attached to hub - a 10-ft heavy-duty USB extension cord that acts as a detachable tether. (this and another wire with power for a USB LED light are covered in light-blue woven cable jacket)- top keyboard/mouse is wireless, but could have a used 2nd USB hub/extension cable- top design allows swapping out keyboard/mouse easily for other computers- small black plastic frame on left is a 3D printed phone holderBTW, I didn't feel the need to modify the recliner arms in any way. This rig sits there rock solid on its own, just had to make sure the bottom was smooth so it didn't rip up the fabric in the chair.If you made something, please share a picture, I'd love to see your ideas!Rich

    View Instructable »
  • richfiddler11 commented on richfiddler11's instructable Altoids Tin 1/8" Stereo Mixer9 months ago
    Altoids Tin 1/8" Stereo Mixer

    I'd build it as-is, but replace one of the 3.5mm stereo input jacks with two mono 1/4" jacks (L+R). On the two 1/4" jacks, the ground/sleeves are tied together, the tip of one goes to the tip of the 3.5mm stereo jack, the other tip goes to the ring (middle) of the stereo jack. You shouldn't have to change anything else. Make sense?

    View Instructable »
  • richfiddler11 commented on victoryking's instructable DIY Lithium-ion battery charger11 months ago
    DIY Lithium-ion battery charger

    Diodes will waste a lot of power (0.7V * 1A= 700mW per cell, for example). This article suggests that parallel connection is not a problem per se, but sometimes large parallel packs will have fuses in line with each cell in case one develops a bad short: http://batteryuniversity.com/learn/article/serial_...

    View Instructable »
  • richfiddler11 commented on richfiddler11's instructable Altoids Tin 1/8" Stereo Mixer11 months ago
    Altoids Tin 1/8" Stereo Mixer

    Hi Marc, if everything is built correctly, the cables are all good and the outputs of all 4 synths are good then you should hear all 4. I would suggest the troubleshooting method of changing 1 variable at a time, for example: for each cable in turn, test each one with Synth #1 and input #1. If all 4 cables are good run through the inputs in turn, then the synths. If all of those single combinations are good, start working on pairs, etc, until you can reproduce the problem. Not much fun, but that's how I troubleshoot.. if you're patient and methodical, you'll eventually find the issue. Rich

    View Instructable »
  • richfiddler11 commented on richfiddler11's instructable Altoids Tin 1/8" Stereo Mixer1 year ago
    Altoids Tin 1/8" Stereo Mixer

    As long as the total impedance of the outputs is high, practically you can have as many outputs as you want. No need for a switch. Remember, the output loads are seen in parallel, meaning that 1 low impedance output load (like headphones) will kill the sound for all of them. But you could drive many pre-amp inputs without a problem.

    View Instructable »
  • richfiddler11 commented on richfiddler11's instructable Altoids Tin 1/8" Stereo Mixer1 year ago
    Altoids Tin 1/8" Stereo Mixer

    Honestly, it's not that critical as long as they're all the same value. Lower resistor values will result in less signal loss, but at some point there will start to be some degree of distortion (when you start to get down below 10x the output impedance of the devices, for example), but that depends on a lot of factors. I think 1K ohm is plenty high enough and you could probably get away with half that -- say 470 ohms or higher, and be fine.

    View Instructable »
  • Make your computer UPS last for hours instead of minutes

    Nice instructable, but in the statement "P / V = I 500 watts / 120 volts = 4.16 ampere hours (at 120 volts)" you're actually solving for Amps, *not* amp-hours. The two are *extremely* different -- Ampere is the unit of electrical current flow and Amp-hours is a measure of battery capacity. This may seem like a picky detail to some, but getting your units wrong can mean the difference between something working well vs having it catch on fire/blow up.

    View Instructable »