Tach on a Bench
Printed From: the12volt.com
Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=6629
Printed Date: August 23, 2025 at 11:38 AM
Topic: Tach on a Bench
Posted By: jrilla
Subject: Tach on a Bench
Date Posted: December 13, 2002 at 6:29 AM
Anyone know how to create a tach signal on a bench?
-------------
J Rilla
Owner/Installer
Replies:
Posted By: jrilla
Date Posted: December 13, 2002 at 11:34 AM
Ok, does anyoneknow of a way to convert 12vDC to anything between 1 and 6 volts AC. Or drop 120V AC to between 1 and 6 v AC? Simple ways I am talking about.
-------------
J Rilla
Owner/Installer
Posted By: TomEllis
Date Posted: December 13, 2002 at 2:43 PM
The easiest way for the tach would be to get a frequency generator. The are variable in frequency and the good ones are variable in voltage output. For the voltage change, use a transformer that is rated from 120 vac input (primary) and anywhere from 1 to 6 vac output (secondary). Tom
Posted By: crroush
Date Posted: December 13, 2002 at 6:52 PM
Easy way to go is to buy a AC -DC power supply at the local Radio Shack, but if you are like me and like to build the stuff yourself, then you need a buck converter after a bridge rectifier, however there are A LOT of fine points on how to build/set up the system, you need a good book on power electronics (phil krein writes a decent book) but if you want more information about doing it the long way let me know and I can attempt to guide you. Craig
Posted By: jrilla
Date Posted: December 14, 2002 at 8:06 AM
Craig, I am just like you in that respect, but I actually don't have much time or resources right now to play around with this, since I will be doing plenty of playing once my bench is finished. I was told I could actually use an AC signal that was greater than 6V AC even though a tach signal from a car would only be between 1 and 6 volts. So I bought an 120v AC to 9v AC power cord, but In my ignorance I could not figure out how to hook iy up. There are two wires and I only need one, so i figured i would just try to use one, so I did a test with my DMM as if I were testing on a car, and it seemed to work. However, the test did not satisfy me. Wil it work to just hook up one side of the AC signal?
-------------
J Rilla
Owner/Installer
Posted By: webguy
Date Posted: December 14, 2002 at 10:46 AM
The frequency generator is really the only solution to your project, simply because hooking up a tach to 60 hz output (you are in the US, right?) AC signal, your tach will only read 60 rpm (something like that). But, if you insist, You will need to connect the ground wire of your tach to the other AC line. Before you say, "but my DC power supply is connected to the ground", don't worry. AC can be embedded with DC, but you are not really doing that - you are just supplying the Tach Input lead with an AC signal. Also install a 1N4001diode inline with (cathode/stripe side towards the Tach) the Tach Input lead. This will filter out the reverse voltage sine wave, allowing only the positive pulse to hit. Here I sit, scratching my head, trying to figure out why you would want to have a Tach hooked up on the bench. ------------- Clean tools = Clean work!
Posted By: jrilla
Date Posted: December 14, 2002 at 11:10 AM
Webguy, I want to have a tach hook up so i can test the features of my remoter starter and the model I am using does not have a tachless mode so it assume it will require a tach signal if i want the unit to stay on. Correct me if i am wrong. I am also wondering how the remote starters know when the key is turned to the on position for programming. Does the ignition wire from the remote starter sense the current when the key is turned to the on position. I need to set up something to enter programming mode. I was thinking if I just gave the ignition 12v+ then removed it and did this three time it would be the same as using the key in the ignition. That is how i have to enter programming mode. Any ideas? As far as the frequency generator, what do i need more specifically. where could i get one and and roughly how much would it cost? Thanks guys for the input, anything else you have that would help this bench be more effective and versatile is welcomed. ------------- J Rilla
Owner/Installer
Posted By: radsta
Date Posted: December 14, 2002 at 1:25 PM
J Rilla- I just gotta ask- why not just install the thing in the car and go? I never thought to 'bench" a remote start. What gives? (it's not a secret, is it?) Steve
-------------
victor
Posted By: jrilla
Date Posted: December 14, 2002 at 2:06 PM
I need to test antennas once in a while and I am always getting new models in and I want to know more about them before I put them in a strangers car. Hooking up to a bench takes 5 minutes to completely hook up while a whole installation of a starter alarm combo can take up to 4 hours. I can also test other accessories too. ------------- J Rilla
Owner/Installer
Posted By: webguy
Date Posted: December 14, 2002 at 2:14 PM
Now it sounds like you are setting up a display. But, yes, by applying a 12v+ momentarily to the ignition sense lead of the remote start brain, with the main 12v+ connected, should work fine to put it into programming mode. I did a quick search just now and came across this site (DIY stuff) https://www.jbgizmo.com/page19.html - jerry's - gadgets, gizmos, crafts, and curious things including.. transmitters, receivers, computer interfaces, rocket locators, radio bugs, electronic circuits.. and free plans Here is also another interesting site on Tachs and tach theory: https://4crawler.cruiserpages.com/Diesel/CheapTricks/Tachometer/index.shtml Have fun........... ------------- Clean tools = Clean work!
|